Maybe they've figured out that enabling their employees to stay a few extra hours without worry to finish a deal is worth it.
The goal isn't to eliminate flexibility, it's understanding probabilities. If fully-flexible/refundable flights are 3x the fare of restricted, then in aggregate, the company could have a chunk of consultants throw out their original reservations and rebook later flights, and still save money. Yes- sometimes consultants need to stay longer than planned, but in an age of prioritizing "work-life balance," most consultants are encouraged to stick to their schedule and get back home when originally planned.
And as stated elsewhere, the majority of consultants are relatively junior people whose role has nothing to do with negotiating contracts.