As a cyclist who sees motorists daily, I have yet to see a motorist obey a stop sign.
When I'm stopped, I have to wave cars through when it's their turn to go because they don't understand how stop signs work. (Or assume I'm not really stopped, more likely. Stop signs are a disaster.)
By that do you mean they don't stop, or that they stop for too long to let you through, thinking that you're not going stop at all? (Assuming it's a 4-way stop). If latter, then I could be that motorist as well -- I will naturally assume that cyclists will NOT stop at stop signs (since I have never seen them do so), so I would let them through preventively.
When I'm stopped, I have to wave cars through when it's their turn to go because they don't understand how stop signs work. (Or assume I'm not really stopped, more likely. Stop signs are a disaster.)