The thing is, shows have a budget. IIRC (someone around here might have a better beat on this) was about $1.5 million per episode, but inside of that $1.5 mil you have pay your entire staff (actors included), pay studio costs, lighting, sfx costs, set costs, promotion costs, etc, etc, etc. That $1.5 mil sounds like a lot to the average person but once everything is paid off, you're lucky if you have enough for a 2 or 3 guest stars and a few special odds and ends for that episode. Some episodes might be a little more conservative so other episodes can have a bigger budget.
The thing that actually kind of drives me a little nuts in this whole ordeal is Picard and Co. were generally available after season 3 of DS9 and baring physical actor availability, it would have made a whole bunch of sense to involve the Enterprise more closely with what was going on in the war. Heck, we almost could have used Picard in place of Ross in most situations since --- you know 7th Fleet and all.