I wondered why it wasn't common in BJJ as well, and my guess is that there must be some skill disparity to get ude gatame opportunities. It's really a matter of timing, when uke makes and error or when you force an error. You don't "construct" it they way you might a regular armbar. Like a footsweep, adding more force won't make up for technical errors.
The actual move takes quite a bit of skill itself, so combined with the fact that BJJ people are very aware of armbars compared to Judo people, means that investment towards learning this move gets put off until later or never. You just won't get beginners or intermediates hitting it on each other.