Sure, that's a discussion to be had. But the 5e XP table is designed in a very particular way in order to speed up and slow down at various intervals in order to create a particular experience across a full campaign. I know I've seen devs mention this online (I think Mearls mentioned it back when he was allowed to communicate), but there's nothing about it in the DMG.
I can't be hedgehogged to look it up, but I think it went something like:
- Levels 1 and 2 are tutorial levels intended to last about a session each.
- Level 3 slows down a little but is still pretty fast.
- Levels 4 through 9 are kinda slow, because that's where the game works best so let's stay in the sweet spot.
- Level 10 is a little slower, just before hitting the awesome stuff at level 11.
- Level 11+ are fast because at that point the game itself slows down with all the crazy stuff that's going on.
I found a spreadsheet I had made that calculates how many medium and hard encounters you need to level up* (going by the DMG guidelines). At levels 1 and 2, you need 4 hard encounters. 3 takes 8, and then it's about 10 per level until level 9. Level 10 takes 11, and after that it's about 6-7 hard encounters per level. This kind of back and forth implies that someone actually designed it to be this way, unlike say 3e which has a pretty static formula of 13 1/3 equal-EL encounters to level up.
* Assuming the actual XP awarded are the same as the "encounter difficulty XP". I never understood why an encounter with many weaker opponents gets treated as more XP for the purposes of calculating difficulty but not for actual awards, but that's a discussion for another time.