Are you kidding me? There are zillions of things our computers can't do today that would be absolutely fantastic if they were faster. You could have said the same thing in 1975 and it would have sounded just as silly.
Example: Render a model of an entire real city in 3d, including interiors, to sub-centimeter resolution. Now take that and think up a trillion variations on the theme.
Yeah, more powerful computers allow us to actually automate the things that currently still require a human being to manage.
Although @seanwilson is correct that almost no one needs a faster Excel, faster computers enable programs that automatically generate what Excel was being used to produce based on plain language specifications. That requires a big round trip to a monster server at the moment.
Well I did say "most people". Developers and graphic designers benefit much more but I'd say casual users and business users are seeing vanishing benefits.
Example: Render a model of an entire real city in 3d, including interiors, to sub-centimeter resolution. Now take that and think up a trillion variations on the theme.