I do not doubt that if customers had a choice between "slow" and "fast", all things being equal customers will pick "fast". Customers aren't stupid.
But in a surprising number of cases, either customers don't have that choice (because the market hasn't provided a "fast" solution yet), or all things are not equal (say, the fast solution is fast because it's missing features that are crucial).
And this is why it always looks like customers are content with poorly-performing solutions.