Why do you think Bi-Wiring improves the sound ?

It all depends on your listening preferences like a new cart, or a new set of speakers. I am enjoying my "bi-wirging" experience. Some music sounds more open to me bc my ears are different than anyone elses. Good luck with your search bc it's your search, and it's awesome that it's your search alone

I tend to agree with several other respondents, especially regarding adding terminals to the speakers if they were manufactured with just one set — I don’t think I would bother.  But the Martin Logan 60XT’s I bought allow bi-wiring/bi-amping.  I had one good amp and didn’t feel the need to buy a second amp, but the speaker cables to allow bi-wiring weren’t much more expensive than the standard cables, so I thought “why not?”    I don’t know whether the bi-wiring improves the sound, but it was inexpensive to check that box, so I went for it.

In my experience, my Silverline Sonata-III speakers with biwired cable sound more analytical, even if the cable is warm (like the Silverline's own biwire cable).  

I own bi-wireable speakers. I also had a hard time accepting that
splitting one cable would possibly make a difference. At that time I was
using some heavy gauge, copper Monster wire and planned an upgrade of some kind.
I was in the Kimber Room at a show in 2019 and asked "Who here might best counsel be on which Kimber cable to buy"? The gentleman I asked said "I think I can do that".
After asking about system and my listening style he suggested
an 8 biwire product. A 3 meter run was about $280.00 and could be made and delivered in 3-4 days.  
The 8 wire strand would be split as follows: 3 to treble, 5 to bass.

This was Mr Ray Kimber himself assisting me.

Interesting side note: My counselor/mentor/friend who has the same speakers as I do was recently listening at my home. He was trying to figure out why my system produced better sound than his. He does not bi-wire.
So I feel I have an improvement thanks to the bi-wire.
Did I do a blind test? No. 

Has anyone got some scientific blind test results??

Oddly my girlfriend and I just spoke about this last week while she was painting my fingernails.  Coronavirus social distancing is getting to her.
Digressing.  We have this Plate Lunch equivalent purchase values.  She freaked when I bought MIT biwire cables.  We could have eaten takeout twice a week for a year on what I spent on them.  However, when I installed them, she immediately heard the difference (good) when she walked into the room.  Not even in the sweet spot.  She does have a really good ear.  So we spoke about it. Why?  I gave her my 40 years in electronics reasons why it should  not make a difference.  But it does.  She came up with this ordering take out analogy.  I order shrimp scampi and she orders a caesar salad.  The restaurant puts them both into ONE container (one cable).   DoorDash delivers, she will have scampi on her salad and I'm going to have caesar dressing on my scampi.  That would not happen if they are placed into two different containers.  And the longer the trip, the greater the contamination.
That's a blonde non audiophile thought.  And I now have red fingernails.