They do that because tons of pilots leave the company. In a few months around 30 pilots left. MOstly due to schedule,money and some other reasons. As they say there are always tons of pilots who want to come there and there will not be any shortage. Lots of pilots after getting TR stayed with the BT for a few months, got some time on type and then OFF THEY GO...... Company was spending lots of money on training and retraining. So I see that things have changed now and they want pilots to pay at least half of TR.
I left myself BT 1 month ago from 737 Captains position after being 5 years inside.