You spend a ton of time belaying you partner (with whom you need to coordinate free time, which is a major hassle if you're trying to climb on a weekday as an unemployed dirtbag) or just clipping the rope into protection while roped climbing. Free soloing you get to do nothing but climb. There's ways to toprope solo so you can just flow up a route without having to fiddle with any of your equipment while you're climbing, but even that will require you to spend a solid 25% of your time rigging (and that's assuming you're efficient, a lot of climbers don't rig very efficiently). A rope team will climb about 3-4 pitches of moderate difficulty in an hour if they're efficient. A free soloist can easily get this done in a quarter or a third of the time. You climb a whole lot more and you get to only climb instead of working with ropes.
Your average roped climbers at a crag might get 3 pitches of climbing in an hour (sometimes even less when they're on hard stuff where they flail). You can get that done in 15 minutes free soloing. After climbing for a while there's a lot of terrain where you know the odds of falling are minuscule, and you know exactly when you feel insecure and have the option of backing off by down climbing. It's a very common practice among alpinists, where moving fast is an enormous advantage and the terrain usually isn't difficult compared to current sport climbing standards.