Again, see above - it's not about 400 amps per se ... it's about putting in bigger wire because we can't predict the future.
It's spending a small additional amount now (on wire) to avoid an enormous expense (trench digging) in the future.
Oh, and you know that 3" conduit required for the 400amp ? Make it 4".
Oh, and you know that trench you just dug ? Throw in double 1.5" and double 3/4 conduits right in there with it.
Oh and you know that first two feet of dirt you filled in ? Now throw two more 3/4 conduits on top of that because you never know when a common carrier on that same pole will have fiber up on it ...
The future could also look like large batteries on-site that charge slowly, and then provide power at high amperage when needed, like slowly compressing a spring, then suddenly releasing it.
This is already what Electrify America and Freewire (https://freewiretech.com/) are doing with EV Fast chargers when the electric utility can't provide a higher power connection in a reasonable time-frame. As battery prices drop, that could be a viable way to power heavy home appliances.
It's spending a small additional amount now (on wire) to avoid an enormous expense (trench digging) in the future.
Oh, and you know that 3" conduit required for the 400amp ? Make it 4".
Oh, and you know that trench you just dug ? Throw in double 1.5" and double 3/4 conduits right in there with it.
Oh and you know that first two feet of dirt you filled in ? Now throw two more 3/4 conduits on top of that because you never know when a common carrier on that same pole will have fiber up on it ...
Future you will be very happy you did.