Because if it’s not fast, it’s not worthwhile.
Because if it’s not fast, the customer won’t buy it.
Because if it’s not fast, someone else’s will be.
Because if it’s not fast, that means it’s not good.
There are so many other ways to measure what you build for someone. Performance is good, but it’s not the only metric.
Don’t let your work be evaluated by one metric and make sure everyone knows all the others that are available.