Sure. If you have a couple of short outages in a year and say 2% of your customers view the website during that time, half quit and never come back over it, that's it. You've lost 1% of your customers.
You seem to be stating that any loss at all no matter how small is a complete disaster without really qualifying it. Yet one could easily make the point - well, what about the customers you don't serve at all because they want to buy a rucksack and you don't sell them? That number could be far higher than the ones affected by outages.
I think this probably just depends on how big the numbers are to be honest. Yes, if 1% of people are millions of dollars, then sure, we care. Usually it's not anything close to being like that.