Because sometimes cloud servers are very cost effective, easy, and fast to deploy: Digital Ocean for example.

$40 / month for 4gb of ram, 4tb of transfer, and two cores, is very cost effective. Linode is also very reasonable.

If all I need is that scale of computing, what should I use instead that makes sense other than cloud services? Setting up colo or a dedicated box for that would be more expensive and a much larger hassle.