Not least because better performance means less money spent on hardware, power, cooling, less space occupied in the datacentre, etc etc.
Joe Hacker might not care about performance of his scripts on his VM he's got from a hosting provider, but you can bet they care a great deal about how many VMs they can fit on one physical host.
Joe Hacker might not care about performance of his scripts on his VM he's got from a hosting provider, but you can bet they care a great deal about how many VMs they can fit on one physical host.