Why do you even have to buy things on the PBE

I used to want a PBE account badly, so when I heard that the PBE signups were open again, I hopped on that immediately. However, I was disappointed that I had to wait to buy everything. Why do we have to wait to buy things? Why do we even have to buy things?

Why can't Riot just give us every champ, skin, and such. This system of having to wait every day to get your RP reset isn't enjoyable. Just give us every champion/skin.