Wife bought one about 10 years ago, would use it occasionally (when legs felt tight and tired after cycling the previous day, it helped, but a easy cycle or walk had the same effect.
As I haven’t cycled for 3 years due to ill health, it was pulled out the cupboard as my legs are becoming tired & painful when walking up hill and it helps me.
If you exercise regularly I don’t think you need it.
If you don’t exercise it’s good for your legs.