Fnord hit the nail on the head:
For me, real time with pause is pretty much the best of two worlds (for party-based games):
With pure real time, you can't really take your time, plan and give detailed orders to the party, and things that are not easily accessible right away don't get used much. This is for an example why I never bothered using any spells in Ultima 7, it meant digging through the spellbok in combat, and that was just annoying to do.
On the other hand, with turnbased, you need to constantly give orders to your characters, even if it's just "do what you did last turn". This can make fights rather tedious, where I just end up constantly giving the "attack" command to my party members.
With real time with pause, the game don't need to ask you when it's a characters turn, the characters will keep doing what you order them to do, until you give them a new order. And when you do want the characters to act a certain way (you want to tell them to cast certain spells, or position the party in a specific way), you can just pause the game and do it. Menu diving is also a lot less tedious when you don't need to worry about a pure real time element.