Whilst a flat infinity edge will produce less damage than a black cleaver and zeal, the difference is very minor, and for each point of attack speed, crit chance and ad with IE scales 50% harder. It's not very surprising that it only takes a little bit more for I.E. to exceed cleaver when considering having the same amount of gold at a later point.
Cleaver is mediocreish because the current meta actually involves a lot of armor. Frozen Heart is a very common top item now. Soraka and Sona are two (if not the two) most popular supports.
It requires multiple auto attacks, and the armor debuff scales post hit, so you aren't even getting 15 armor reduction on the first hit - this means a lot more than you'd think.
Continuing on, the best that ranged carries can generally muster is a minor amount of auto attacks against a coordinated team in most team fight situations, blackcleaver starts looking swell after 4 auto attacks. Infinity Edge in 4 auto attacks can very easily kill a lot of characters assuming an okay critical strike chance. One auto attack with infinity edge can deal 250% more damage, and that's a lot more scary to an enemy tank than "oh, i have 200 armor, now i have 160!"
Cleaver is an okay item in terms of dueling - which is obvious. But it just doesn't have the utility required in team fights to be worthwhile. Bloodthirster is giving more damage (and a lot of ranged carries have AD scaling on their abilities) and life steal, which is allowing dem ranged carries to last longer in fights and actually be able to handle 1v1ing against tanks/bruisers (You'd have to be pretty fed / well taken care of for you to take no damage while stacking up cleaver). Infinity Edge is plainly allowing you the ability to be able to kill carries in 2-4 auto attacks, which competitively, every auto attack counts, A LOT. Black Cleaver has a hard time fitting.
At least on ranged carries.
There's some good usages of it for some melee characters (and this actually is a more beneficial situation because someone who is 'tankier' who scales with lasting longer in team fights rather than each individual auto attack will be reducing armor for the ranged carry to deal even more damage), but that's about it.
Ezreal and Corki have "acceptable" usages of it. Ezreal being all applying 2-3 stacks of with reasonable instantaneous actions. Corki having his aoe armor shredder, plus no auto attack steroid, plus the extra armor shred from cleaver can really really wreck people. But in those two cases, they're short sighted gains (I suppose a good early item if you're at a nice lead so that you continue to wreck ****). But, assuming you always have a lead is silly, and if you're trying to farm to survive and become a threat later game, Infinity edge and bloodthirster are providing a lot more.