Main reason is there aren’t that many bleed skills in the game. Even less skills that have substantial bleed worth building around, as opposed to some skill’s “flavour” bleed (looking at you Primal Strike, Forcewave and Bloody Pox). Then even less skills that are cool to level with (transmuted Blade Arc is viable endgame but levelling with 5 sec cooldown melee skill will feel like shit). Add in that some skills just don’t have much budget support (Counter Strike, Vire’s Might) you’ll have our current situation when noone just bothered to make such a build.
I can vouch for only one bleed build that feels decent enough to level - it is the blade spirit build with Scarab Shell. E.g. this thread. There are even some levelling tips down in the comments.