You don't understand encounter design or why the numbers are the way they are then.
Let's explain.
Take your level, and see the amount of XP you need for your next level? Subtract from that the XP for the last level.
Don't argue, just do it.
Now let's say you are level 6. To reach level 7, you need 10,000 XP. To reach level 6, you need 7,500 XP. That means in order to go from 6 to 7, you'll need a total of 2,500 XP.
Looking at a typical level 6 monster, let's say a Tiefling Heretic, we see that it gives you 250 XP.
Wait.. Level 6 monster, 250 XP... need 2,500 XP to gain level 7.... but if that XP is divided, that means we have to kill 60 monsters! UNFAIR! UNFAIR!
Now hold on there bucko. Before you start saying how it takes 'forever' don't forget, you're not fighting these monsters one at a time.
An equivalent level encounter is considered one monster of your level for each member of the party. So if you have six players, that's six monsters at 250 XP each. That comes out to 1,500 XP for that encounter.
However, not all equal level encounters are exactly six monsters. So long as the XP totals of all the monsters equal 1,500, the XP budget will make sure it's an equal level encounter.
And not all encounters are equal level, some of them are challenging and have higher XP budgets.
Regardless, if n is the number of players, then a standard encounter gives xp = Number of players X (XP needed for level) / 10 total. Then, you divide that by number of players... and you get exactly one tenth of the XP you need to level.
In other words, the XP system is designed so that after 10 regular encounters, you gain a level.
'But that's a long time!'
Suck it up princess, that's a less than 3E's 13.33
And don't even get me started on previous editions and their money-based XP system.