I think I have experienced this at past companies, including Amazon.

But the limit was very high. I recall setting the contribution to something like 80% or 90% and maxing out after a few paychecks.

But in general: I agree with you. Why should we only be allowed to do what my employer allows? As if them allowing me to contribute is some benefit they are bestowing upon me. Rather than them just being middle-men between me and tax law.