When the game starts to break down at higher levels, people tend to stop playing it.
I ran AD&D, through both 1e & 2e. That campaign ended at about 14th level. I'd so heavily-modified the rules I don't know if it was legitimately D&D anymore, but I did get it to go 14 levels.
3.x, similarly, the campaigns I was in all gave up the ghost before 14th, some before 10th. One that started at 15th didn't last long enough for anyone to reach 16th. The two that got closest to 14th ran 6-8 hours a week, 3 months a year (alternating with eachother, other D&D campaigns that folded quickly, and my own Champions campaign) for the full run of 3.x.
Mechanically, most versions of D&D just had a 'sweet spot' where they worked well. You slogged through the fist level or few to get there, enjoyed the mid-levels, and then the campaign broke up, or characters retired or you otherwise re-booted back to playable levels.
I don't know if 5e plans to be an exception to this phenomenon. The way it's designed to have characters level very quickly at first, slow down, then level quickly again around 11ths, suggest that it /has/ the sweet spot, and is just designed to linger there, where powering through the levels that bracket it.