Cause they don't want you.
They want to choose there own pilots and control thier training from the word go. And part of that training is flying a TP for Flybe as an FO they don't want LHS to RHS CRM issues. They just want to get the pilot up to speed with approaches and landings in a CAT enviroment then move them on to something heavier.
It could very well be that 5-6 years worth of pilots are stepped over. With no chance of coming away from turboprops and regionals.
And I wouldn't mind betting there will be some word of mouth deals going on so the larger jet operators don't screw all the TP operators up again like when easy jet started hoovering up the market. Which basically screwed 3-4 companys for 2-3 years by stripping there TP Captains sometimes with notice being handed in on the day they had completed line check. Bonds didn't mean a thing guys were doing 500 hours and then legging it. Training deptments couldn't keep up with the numbers leaving.