BotRK is not an ad carry item, ad carries don't build cutlass to begin with. It's for autoattacking bruiser champions with low (but existent) ad scalings and built-in attack speed steroids. It's very good on Nidalee (Q scales up to 3.0 with AD), Jax (Q and E scale), Tiger Udyr (Q scales 1.5 with AD), Nocturne (Q, R, and passive scale), Warwick (R scales 2.0, W gives huge attack speed).
The problem used to be that only ad carries could kill tanks at all. BotRK somewhat solves that by turning you into warwick, where you can kill any tank given enough time thanks to your sustain. It's not a burst item, it is an item for bruisers to duel tanks. If you are nidalee with teleport and you need to stop the 4k hp Shen from splitpushing, you get BotRK. That is an example of when you should buy it. The decision to not let it scale with crit indicates that ad carries should not build this item.
As for attack speed steroids - sure they scale BotRK... but they scale BT equally! That is, if I have 40% attack speed, that increases the worth of both BotRK and BT by 40%. Their relative value doesn't change at all.
Basically, we have two approximately equal items - BT and BotRK. They are similar, but one is slightly better in some situations, the other slightly better in others. BUT THEN, there's a whole statistic, an entire category of items and effects, that affects one but not the other. Even putting aside balance issues, it's really ****ty design. All the auto attack stats and items reliably and intuitively multiply each other's power - except BotRK, which, let's face it, almost nobody builds EVEN when everyone is stacking HP! We're basically living in the ideal meta for BotRK and still nobody wants to build it because it loses literally over half its power by not scaling at all with crit!