You are absolutely right, but this is not a problem of Schiphol (or the principle of security at the gate) specifically. It's a problem of even having these stupid checks in the first place, and them having gotten worse and worse over time due to government stupidity, especially on the part of the Americans and the British. The security checks are a pain in the ass in any airport that deals with flights to either of those countries.

Of course with security at the gate you will always go through it again when at Schiphol (which is only once btw, the first time was at your originating airport), but there's no real need for it to be such a hassle.

Here's another thing to think about: what's stopping foreign governments (especially the US) from requiring that all international passengers be checked at the gate for flights to their airports some time in the near future? With central security, you'd have to be checked twice at the same airport in that case. And frankly I wouldn't be surprised if this were to happen at some point.