Probably just because it's cool.

I'm sure there's some bean-counter calculus involving recruitment, PR, demonstration of capabilities, they were going to be doing training flights anyway so why not do a few in public, etc. but they're more rationalisations rather than reasons.

I hope it stays that way too. A world where we take everything away unless it fits into the 5 year ROI spreadsheet sounds dreadful. In any case there'll a long tail of nth-order outcomes that we can't simply reduce down to a risk-reward calculation.

There's probably some deep reason why humans just have a drive to show off their awesome stuff.