Well it affects your game every single tick. There is stuff that needs to be there. Position updates for example if a character is moving automatically.
It always depends on how much you put in there. As general rule you should take this: You can avoid using it? Do it. Use events as much as you can.
Small stuff hardly affects it at all but the less is in there and called less often the better your performance will be.
For shooting for example. You don’t have to use tick but can bind it on the time.
Also you have to consider that tick is variable. It can have different amount of calls on each computer you run it so you shouldn’t use it at all for gameplay relevant stuff.