The short answer is: TR plans are, generally, geared toward people with limited time to train, so it (intelligently) replaces volume with intensity.
That being said, I would also guess that you may not have edited your plan, if you actually have more time to train each week (or would just like to train more because you love riding your).
For me, the key pieces of data used to build the training program are: type of event, length of event, intensity of event, how ‘aggressive’ you want the training plan to be, and how many hours (each day) you have available to train. Once you set these up to your liking you should be good to go, though you still have to trust the app.
This might be a good place to start: https://support.trainerroad.com/hc/en-us/articles/360037923191-Plan-Builder-Overview
Step 5 is probably what you want. (Just keep in mind that if you, for example, put in that you have 3 hours available to train every day that you likely won’t actually be scheduled for 3 hours of training every day, though TR might eventually build you to that, if you are actually handling the load reasonably. So, put times for each day that are truly reasonable for your schedule.)
I’d also recommend that you run the ‘Check Volume’ utility occasionally to see what it recommends (you always have the option to say ‘no thanks’).
Personally, when I started with TR (which was only a few months ago), I felt much the same as you. As TR has gathered more of my training, though, my volume, which started at 7 hours of training over 5 days of the week, has changed to 11 hours a week over 6 days. And, honestly, I feel like my cycling fitness has improved quite a bit. (And, as a side ‘benefit’, I’ve learned that I can handle Sweet Spot workouts pretty well, but Threshold workouts kick my ass, which will help me to better pace myself during events).
I hope that’s of some help.