In the snake world it's called a "breeding loan". While it can work out if both parties involved understand that not everything goes smoothly and Mother Nature is a female dog, all too often when stuff happens one or the other party feels cheated on the transaction and friendships end.
You have to remember in the livestock and dog worlds there are industry standards and practices that have evolved over hundreds of years. The reptile pet trade is relatively young in comparison - only a few decades old - and practices are still evolving.
Add to that the logistics: someone with a nice male will want to put him to a lot of females during the season. So, like with horses, the female travels to the male. Unlike with horses, any reputable snake breeder will want to protect his collection by quarantining the female for at least 90 days, maybe longer, while a mare can show up with a negative Coggins and a health certificate and be put to the stud on her next heat cycle.
Once a female snake is gravid there's the problem of moving her back. Due to stress I wouldn't subject her to shipping, I would want to go get her, so I'm limited in the studs I can select to those within driving distance. Once she gets back I also have to quarantine her for 90 days to protect my snakes from anything she may have picked up from the stud owner's collection.
OTOH back to horses - a gravid mare can safely travel until she's just a few months from foaling, and most horses learn to not worry about being shipped.
The owner of the snake stud has to trust that I will incubate the clutch correctly, that I will not lie and say the female slugged out, or she laid six eggs when she really laid eight, or she just didn't go, etc. if the contract states the clutch is to be split 50-50. The stud owner can mitigate that risk by charging a flat fee so he gets paid even if there is no clutch, but then he will feel cheated if the female throws a spectacular clutch and he opted not to take a 50-50 split, and owners of females will feel cheated if they pay a flat stud fee and there is no resulting clutch, or if the odds gods aren't kind.