Being booked out 2-5 months ahead is typical for us. Two weeks is effectively zero notice period because you'll almost always have more remaining days of paid time off than that. If we had to account for N people being able to leave effectively on the spot, we'd not be able to sell more than 8-N persons concurrently (we're a small team), at least not more than a few days ahead. At N=1 person, that's already 13% lower turnover for the whole company.

After the trial/probation period where this notice period is not in effect, when I know what the employment is like, I'd much rather get a 13% higher salary and, should I choose to quit, wrap things up properly and do the job for 2-3 more months. (The notice period is not as long as we schedule ahead for: with 2 months' notice, we can find a good freelancer and get the paperwork done without time pressure, or the client can still find another firm in the worst case.)

Since I was fine with doing this job for years now, those months seem insignificant for the benefits that go both ways.