Why do dogs get stuck when they do it?????????/?

Question

Why do dogs get stuck when they do it?????????/?

Answer 1

When the male dog mates with the female his p***s swells after ejaculation and prevent him from withdrawing.  This prevents other dogs from enseminating the same female and ensuring that his sperm produces offspring.  Hope this helps.

Answer 2

It gives the "deposit" from the male a greater chance of being the only "deposit" in the female while she is in heat.  The longer they are "stuck" the less chance another male will come along and make a "deposit".