1) They probably have a huge amount of data. Moving it without downtime might be an extremely costly and long process. 2) Cloud providers aren't generally that

1) They probably have a huge amount of data. Moving it without downtime might be an extremely costly and long process. 2) Cloud providers aren't generally that great for IO intensive application, I don't know if they use something like FusionIO cards, but if they do, it might be hard to get analog IO performances on cloud providers (i3 on AWS are quite good at that however). 3) If you can front the cash, manage the logistical aspects and have a relatively constant load and defined core functionality, bare metal is way cheaper.