Leveling in Battlegrounds

A friend and I farmed a complete set of heirlooms to start a PvP journey as rogues (pls don't judge).
As we were accustomed to starting in cataclysmic back in the day and later expansions, we got exp while doing battlegrounds. However, when we started our journey and joined our first battleground to start leveling (LVL 14) we experienced after winning the battleground that there was no EXP!

I asked in the global chat and searched on Google if that was true or something else was the case.
From Global, I got the answer that there is EXP, but most likely only starting level 70.
From Google, I got the answer that EXP was added in 3.2. However, it was not clear from which level.

What is the reason that there is no EXP in Battleground all the way up to level 80?
Is it because it was like this in retail or does it have another reason?
As we could see no harm in adding this feature as it would ad another way of leveling up and enjoying the game!

I would like to hear your opinion :)