When using a power conditioner, why is it advised to run amps directly to the wall?

I guess I am lucky to live in a location where power noise issues do not seem to be noticeable, at least in my system.  I do understand how power issues may be more noticeable to folks who live in multi-family condominiums or apartments with shared power, and suspect the effect of conditioners might be more noticeable in some of those situations.

In my system, dedicated 20A circuits, 10 awg Romex in the wall, good outlets, shielded power cords of sufficient gauge using noise cancelling geometries and good connectors, and components with well-designed power supplies seem to be sufficient to keep power line noise below what I can perceive. I do power my front-end digital gear from an Isoclean 60A3 II that is mainly used to provide multiple outlets rather than for any conditioning. 

In the case of my amplifiers, those are plugged directly into the wall and have no on-board power switches or in-line power fuses.  However, in the wall, I have wired two thermal magnetic switches (one per amp) that are exactly as used by the amplifier manufacturer in their most current amplifier designs.  Those serve as the on/off power switches and protection for the amplifiers, since they do not have on-board switches or fuses.  The power cord length to the amplifiers is 1 meter and I have tried shielded and unshielded power cords with no perceivable difference.

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I bought a PS Audio P15 last year, after using Furman Elite and a Puritan PSM156,  and plugged everything into it. It has improved my system and I am happy with it. I purposely plugged my amp into it for a couple months, and then switched it to the wall, a noticeable and positive difference. Why, I do not know, but that is the case, probably current limiting, though the specs on the P15 say that should not be the case.

@cueball9

Thanks for finally mentioning protection in the event of a power surge!  I wondered when it would come up. The power in my area is fairly unreliable and goes completely out several times a year minimum. It’s so bad that I installed a whole house generator last fall. I’m concerned about frying my system as a result. 
 

I am sold on the idea of installing dedicated power runs to the system after the many mentions and recommendations for that. As my system is in a basement man cave, the main panel is just a short distance away. It would be cheap insurance. I have a good friend that is a professional electrician who has worked on my house several times too. I will get right on that one. 
 

And lastly, the McIntosh MPC1500 is not an inexpensive unit. It was $5,000 back in 2009 when I bought the whole system. I think it’s around $7,000 now!  The comment was made that you get what you pay for. I would like to think that what I got is pretty good. And also mentioned is the synergy with all the other Mac gear.  But I will contact McIntosh for peace mind. 
 

Again, many thanks to all for your guidance. 

I wanted to add more to this discussion, if I may.  If current is restricted voltage will drop.  That’s it.  If the voltage remains stable then the amp is drawing as much current as it can. 

After YEARS of watching AC  power fluctuate in apartments and my home the biggest problems I have seen are NOT the amount of power your amp draws.  The biggest problems are daily / seasonal variations in AC voltage and what your big appliances like your HVAC and electric range or hot water heater are doing.  The device in your system that’s going to be most susceptible to this is a linear amplifier. 

For this reason I take two approaches.  One is I use a cheap ($12-20) voltage meter or conditioner with a voltage meter.   Plug it in and watch your voltage sag or not.  Especially useful with these is to watch the N-E voltage as it may indicate voltage restrictions due to wiring length.  

The other thing is I use an actual voltage regulator and surge protector at the front of all my home entertainment systems.  The most expensive versions are from PS Audio, which regenerate power.  For that reason and that I live in a lightning prone area I use Furmans with series mode protection (SMP) and voltage regulation like this one (yes, this is an affiliate link).   It’s ridiculously less expensive than a PS Audio unit with similar power rating. 

I know some surge strips offer damage warranties, but my amp is 60 lbs I do NOT want to pull out and ship and wait for repairs.  Also storms sometimes pop up without warning.  While it is good advice to unplug equipment, half the time things happen I am out of the home or don't have time to react before it's happened.  

" I have had literally everything in my rack plugged into the Mac power center for nearly 16 years plus I just added a big powered sub a few weeks ago. It sounds great and I have had no problems at all."

That says it all. Your ears/practical self rule. Now you're brain washed with yes/no/maybe...

Get out now while you can-with your wallet intact!

"I am sold on the idea of installing dedicated power runs to the system after the many mentions and recommendations for that."

Maybe the #1 thing to optimize what you already have. Don't forget to finish it off with fancy audiophool approved outlets too. You may not even hear a difference/improvement. 

If not, confirmation to just enjoy your setup.