I couldn't disagree more. I was playing around with AWS when I was probably 14 years old, with a credit card from my parents with consent, and a strict budget and the understanding that if I mess up and overspend, I'm getting disciplined.
I learned a lot of stuff about networking, how AWS works (VPCs, IAM, CloudWatch, etc) from trial and error, and hobby projects like personal websites (free tier), hosting a Minecraft server, etc.
Being too overprotective can have negative consequences on folks who are responsible. One of the things I love about the technology and internet communities, etc is that you're mostly judged based on how you act and behave; not your age or other visible characteristics.
Some variant of this topic comes up with some regularity. Leaving aside technical issues associated with implementing real-time hard caps, you still have a tradeoff. You either implement hard cutoffs which a student or someone else on a hard budget would like. Or you have a situation where an admin (or an admin who is no longer with a company) stuck some number in that seemed sensible at the time that brings down the company's whole system because of some sales spike.
I get that (and why) some people won't use AWS or its main competitors for this reason. But, frankly, they're not AWS's market and AWS will basically shrug.
The equivalent 10+ years earlier was so much lower risk: £25 or so for an old computer at a junk sale, £4.99 for a magazine with a Linux CD-ROM to avoid a week-long download.
> strict budget
How does that work in the case of AWS? Are you confusing alerts to caps?
You don't have to use AWS though. Get one from Digital Ocean or Herzner, they have very predictable billing. Any button that costs money will tell you how much it costs per month.