You don't need as much power as you think you do, unless you want to have senseless "fun".
If cost is negligible, and bike handling/performance is not otherwise hindered by additional power, I say why the hell not. You don't have
to use the power. - But you've got it if you want it.
I can think of three reasons not to use more power than you need. First, even if a more powerful motor and controller cost the same (ish), the battery required to feed them will cost more at a minimum, and range will be reduced for any given battery.
Second, if the power is there, you will use it, and the risk of accidental/negligent injury rises exponentially with added speed and power. That's not a reason to totally avoid a high power bike; but it is something to keep in mind, especially when using a vehicle that was only ever meant to use muscle power and may be less than totally competent under motor power.
Also, if you keep power modest, in most places that means you can treat the thing as a bicycle in terms of licensing and registration. That reduces cost and inconvenience. Using more than the allowed amount of power in an unregistered vehicle is illegal and unfair to legitimate road users who meet their obligations. The street is a public resource and we don't all get to pick which of its conditions apply to us.