Why so many tubes?

Was this a troll thread?

Who cares the platform as long as it produces high quality reproduction of music?

I thought that it was like 💰 money. The more the better!😄

You need to use a lot of power tubes if you want crank up the output without putting a really heavy burden on each tube.  So that's why you see the 100w tube amps often use an octet for example.  Not my cup at all as I prefer lower output triode amp paired with high efficiency/easy load to drive speakers.  But the technical explanation is simple...to the point this does feel like a trolling thread. 

There are always different ways to approach a task.

If you want simplicity in the signal path, start with high efficiency speakers, dht single end triode integrate amp and a source.

more watts require more tubes. 

I don't use high power (Lamm ML2 SETs in the main system) but everything from phono stage and power supply to line stage to amps is tube circuitry so I do use a lot of tubes. That in itself is not a problem. (I like to think of them as "field replaceable" parts that solve some, not all, problems). The difficulty is finding good sounding tubes that satisfy--and in that, I don't mean to be a snob-- to the contrary, a modern circuit that can work at optimal level with current production tubes would be preferable to having to hunt for increasingly scarce, and expensive, NOS that is fresh. 
With tube gear, I've had pretty good luck since the early '70s with medium powered amps (70 watts or less) and minimal issues with tube preamps. My current amp set up is the above Lamms-- pretty simple and lower powered at 18 watts per amp-- or in current operation, some restored Quad IIs running real GEC KT 66s. 
I haven't counted how many tubes are in circuit in either system, but it's probably a lot. I replace/refresh when necessary. It's part of the routine operating cost of tube gear, with the above caveat about sonics and NOS/scarcity and cost.