I hate to say it but it's a cost/service delivery issue.
The hotel looks at the night shift as a dead end. Multiplies the wages, multiplies 365 days, times the number of hotels in the chain and comes up with a number thats too tough to bear.
Compounded with service delivery. For the customer, speed of delivery for breakfast is the most important. Throw in 20, 40, or 50 orders for the same time and you've now got that many potential scr*w ups and that many angry customers.
IMHO Hotel chains hate spending money on wages, and delivering service that costs money. They also don't like creating obstacles to a guests service perseption. They'd rather not offer it, then have you upset at what they've done.
Just my 2 cents. Hotels aren't about guest service, not anymore.