It can absolutely lead to jail. Don't pay the fine in time, suspended license. Driving on a suspended license? Arrestable offense. Miss your court date? Warrant. Even if you go to court and they put you on a payment plan, that gives you a few months to pay it, costs even more, and if you don't pay in time you've violated a court order.

If you don't pay a probation fine in time, you can quickly go right back to jail to serve the remainder of your sentence.

Yes, multiple civil infractions can lead to criminal ones. That's what is suppose to deter people from habitually committing petty offenses.