PvP requirements

I understand that right not there's level max limit for act1 PvP. What I do not understand is why there is a quest requirements for it.

I leveled a char till lvl28, killed Vaal and crossed to Cruel difficulty. Came back to act2 normal to play PvP and I can't participate just because I entered Cruel dificulty(and I'm just lvl28)

I fail to understand the logic behind that.

Because there are questrewards.

Because if you could pvp in lvl 28 after going through later difficulties then EVERYONE would have to get rushed through them all for the bandit rewards and skill point quest rewards, in order to be able to compete with other people who've done that.