The main reason for that is time traveling and dimension hoping come at a tempo disadvantage. When you create a new timeline, you make 1 move, but give your opponent 2 moves. You used your turn in the present, and created a new board where it's their turn in the past.
Any time travel or dimension hops need to be worth twice as much, minimum, as a normal move to even consider making them.
It does have more depth than normal chess, but it's not infinity deep. I still love it. My biggest concern with high level chess matches is that many, many games end in draws. It feels like it's impossible to a draw a gam e in 5D chess' [0]
[0] https://www.reddit.com/r/Games/comments/hxqo6d/how_to_play_5...