Because...
- It takes time to deliver supplies from your systems to the frontlines.
- Said convoys would be a prime target for attack. One thing that the enemy would do if you go on the offensive is to try to sneak a squadron of frigates (possibly with a freighter for resupply) or a light cruiser behind your lines to raid your convoys in attempt to stop your advance.
- Even if they can at least slow it down and force you to commit ships to intercept them and escort your convoys.
- Most freighters are slower than warships at FTL speeds.
Having a mothership means that a fleet far from home is able to better keep up its strength and lessens the requirements. Moreover it would be in a position to produce more topedoes or shield generators and have them on hand if there is a pressing need for said things without waiting months for it to arrive from the main shipyards. It can also be useful in setting up support bases along the way.
Torpedoes and fighters have an maximum acceleration of 40g, gunships have a top of 30g, covettes and destroyers have a top acceleration of 20g, for destroyers and cruisers its usually between 18 to 12g and battleships have a top acceleration of 8g. Both superships can match a Battleship at STL speeds. Drive systems are gravitic.
Yes, interdiction fields can force ships out of hyperspace and make them do an emergency transition back to realspace.
Zor