As well as all of the above considerations, it seems to be A Thing that huge numbers of women feel massively ashamed about having a poo in public toilets - and also about people knowing that they've had a poo and/or smelling the proof of it.
Therefore, there must be a lot of women who, when they simply can't avoid having a poo in a public (or work) toilet, get to the front of the queue, get a a cubicle, stuff lots of paper down to lessen the splash sound, have the poo (maybe waiting until somebody coughs or flushes), then wait until the smell has dissipated and/or it sounds like everybody has left and so they can sneak out unnoticed. Therefore, a poo alone could potentially take 10 or 15 minutes: 1 minute for the actual poo and the rest for mitigating social embarrassment at having the poo.
By contrast, the men who need a poo probably all go to the one or two cubicles (which are not already taken up by men who only need a wee), promptly and noisily drop their guts without a moment's thought, wipe, flush and walk straight out with at best a half-hearted "Sorry, mate, it whiffs a bit", no comment at all or even a proud smile on their faces.
They also know that, if there's another man waiting for the cubicle as soon as they emerge, he most probably is going to have a stinky poo in there too, so he's hardly in a position to judge or blame them for having just done the same thing. If men actually cared or felt embarrassed about the smell of poo and were in the habit of judging and being judged for having a poo in a toilet, the judges would be over at the urinals and not in the picture for recriminations at the cubicles anyway.
The only occasional bottlenecks are probably caused by shy men using a cubicle just for a wee or men taking their young children in with them who are either girls or boys who are too little to reach/not confident with using urinals.
If you're at a performance aimed at little children, and there are a lot of dads taking their kids to the toilet (and not leaving it to their wives to take them), you'll likely find that there's quite a queue for the men's too (although they'll still have set up a 'fast lane' for men without children with them who only need a wee).