Interestingly, it is not mandatory to wear a parachute in a glider, passengers who are large and heavy are quite often flown for weight/space reasons without a 'chute. However, even though the cost and maintenence of them is high most flights are taken with a parachute, the risk of collision is higher especially on a cross country flight because any glider thermaling attracts others and you don't see them all.
A low wing aircraft with a decent canopy jettison should be easy to exit but a high wing aircraft that is out of control would be more challenging, all of that is assuming you have enough height for the canopy to open.