Trails has a little "drawing delay" if you want them to change location and if you want to remove a trail, the effective and fast way is by using the "Clear" block, but it clears all the trails so you would have to re-draw a lot of trails just to remove a singe trail.
And, to get trails interactive, you would need invisible text because there is no "When object bumps trail", like there are with shapes and text.
These aren't necessarily limiters to creating a game entirely from trails. Though one would have to ask why that would be advantageous.
The game would need to be setup where each trail was a separate text object and all trails would redraw every frame. Collisions could be done with math.
Since the Hopscotch Player quality & performance is rubbish I've been making games that entirely avoid (or at least minimize) the use of bumps. Most recently I've been tinkering (not yet published) with a high performance version of Break Out:
No When Bumps are used anywhere in the code. The collisions (with the edge, bricks, and bumper) are done entirely with math. This is done to avoid lag that's inherent with When Bump events. It's a shame that we can write higher level code that detects bumps more efficiently than the Hopscotch Player collision engine, but alas that's just the current state of Hopscotch.
Anyway, I digressed. The bricks and ball use Shape objects, but since there are no When Bumps, those graphics could also be created with dynamic trails. However this would require the same number of text "pens" as Shape objects so I don't see any advantage to doing that.