ADS-B why

I agree, ATC and local glider ops know jet routes. Where I fly (Middletown, NY) is right under a jet route into Newark airport in NJ. Jets usually come through at 6000'MSL south bound.
Many years ago we had a great soaring season with students getting to 10,000'MSL on thermals, thus above jet traffic. Boston center called our airport and "complained" about glider traffic. Reply back was that we had "right of way" in that airspace.
Now ATC brings jets through above cloudbase on weekends for separation. We teach to look towards the NNE now and then when getting towards cloudbase to look for traffic that wander below clouds.

Our other two concerns is a VOR on the ridge NNW of our site (about 20 miles out) and C5A traffic from Stewart airport east of us (about 20 miles out as well). On weekends, the C5's stay east of a local highway, we tend to stay west unless we're high since they are shooting instrument approaches using the VOR as a steer to final approach.

Similar for HHSC and Corning regional airport.

Bells and whistles are great, but looking outside plus knowing where big fast traffic will likely be is a great start.

My two concerns regarding midairs are someone doing something unexpected in a thermal (bells and whistles are likely too late then) I'm in or flying in the wispies at the bottom of a cloud where the low light and grayness totally hide a glider visually.