You can get servers elsewhere as well and they can be more agile than Dell/ HPE/ SuperMicro/ Lenovo. Asus, Asrock, Gigabyte and some other brands can ship servers rather quickly. Perhaps not the next day but the prices are much lower out of the door especially if you are a smaller customer. Most companies know well in advance how much compute/ storage they will need. So if something takes a month or two it isn't a big issue.