Yes, why do some people insist that every element of a service provision should make a profit? It's really rather naive.
DB are currently turning the bistro in their ICE3s into a full restaurant. They have stated that catering makes a loss but regard it as an essential part of the overall Inter-City package. Get rid of the catering and that's one less advantage you have over your competitors.
Businesses - whatever their ownership status - have to make policy decisions about how they choose to spend their money and control costs.
If DB had shareholders who take a close interest in the bottom line to deal with all the time - which is the case for First Group, as opposed to having to answer to the German government - then it would probably be facing a lot of questions at its annual meeting and regular key shareholder briefings as to what it was going to do to stem/eradicate losses, wherever they occur in the business.
DB currently has a debt of about 20 billion euros of debt but was bunged a billion euros to help with losses by the government back in September, on top of a pledge of 50bn euros to fund a 10-year modernisation programme back in March - so it is operating on a different planet from your average British TOC when it comes to financial support for all aspects of its business.
PS: If you have visions of these extra 'restaurant' cars serving food cooked on board by a chef like a GWR Pullman, then please forget it. Bordrestaurant is airline-style modular pre-prepared food straight from the microwave, the same as has always been the case in the ICE3 bistros.
Trolley provision must be less profitable because it requires space for a static trolley service (roughly what a mini-buffet could fit in), space for stock, the expensive trolleys with all the safety messures for operating among passengers, plus then the kitchens are left unused. If that results in smaller losses than a mini-buffet, there is probably accounting tricks like not paying for the static trolley dock and stock cupboards.
The trolley station cum hot water boiler area in the middle of nine-car GWT IETs is the size of a toilet - as it is the same space used for toilets in other coaches, and ever so slightly smaller than the two full window bays and former toilet occupied by GWR's HST mini-buffets. The IET kitchens are supplying the first class at seat offer and also hold extra stock for the standard trolley.