Hey now, when I joined I asked the forum about doing 10c/50 vs 5c/25c and that seemed to ruffle a few feathers lol. I was told to "stop trying to reinvent the wheel" and "why are we trying to fix something that isn't broken?" etc, so surely it's a little controversial (but maybe sentiments have changed since).
So cool!
TLDR for my response below: Starting with T500's is more efficient for a tournament breakdown because you need fewer T500 chips in play which will soon be back in the case at the first colour up anyway.
But
@JustinInMN already covered one of the main reasons being that since you only ever
need one T500 chip per bet, you can get away with having fewer T500's in starting stacks, and when the first colour up comes around you don't lose ~35% of the chips on the table. (ex: T5 base, 2000 starting stack of 10/10/7/2 removes 35% of chips within the first hour of play, where as a T500 base, 125,000 starting stack of 6/12/12/2 only removes ~19% of chips). Most people love having moar chips, and this helps maintain that in a fairly efficient way.
But to expand further on this...there is a positive trade off to having fewer of the smallest chip in a starting stack. If you think about the standard T5 stack needing 10/10/7/x or a T500 needing 10/10/7/x
VS a T500 using 6/12/12/x you are effectively sacrificing the smallest and least valuable chip (the same chip that is only used for 25% of the total gameplay then tossed back into a case) to gain extra, more valuable chips that are used much later on or even to the end of a game. You convert those 4
measly T500 chips into two extra T1K and five extra T5K's which are the early and late workhorse chips, respectively, giving more useful betting chips and having less change making scenarios after the first break when the game is in full swing.
And a much less important reason for not starting at T1000 (or T5000) is that when people make bets or count their stacks they don't use the word "thousand" very often. When everyone knows the context that each chip is already in the thousands they just drop the word and say "3" or "I'll bet 50" instead. Having a T1K or a T5K base tournament is the same as a T1 or T5 base but you've just added on the word thousand for funsies (which is perfectly valid for novelty, especially when you have
@cpac54 Rio set

, but not for a standard tournament, in my opinion). When doing a T500 base set you start the tournament betting in "hundreds" (ie 15-hundred, 85-hundred etc) and then switch into betting thousands later on (5-thousand, 45-thousand etc), so in a way the denominations actually matter a little more and serve more of a purpose.