Bordeaux & Paris transportation

For the trams in Bordeaux, you just tap as you enter (you can buy "tickets" through the TBM app or buy paper tickets at any tram stop--there's a machine.) If you are taking a TER train, a conductor may (or may not) come by to scan your ticket, no tapping necessary. For the TGV train, you will scan before you can get on the platform then the conductor will scan again on train.

In Paris you still need to buy tickets or a pass, but you can now do it with your phone. Paris is a bit a law upon its own. Everybody in Europe is doing tap in using CC, so Paris is not going to do that...

You would think they would do tap in in Paris since one size fits all on the train EXCEPT airports. You could have tap out at airports only or have a separate tap in just for admission into the gate at the airports. I.w. you tape in for 2.50 in Paris, then at the airport you tap in for entry for the remaining cost of 10.50 in order to clear the gate at the airport -