This seems high...I just went through a bunch of front end web developer interviews and nearly everyone I was asked some algorithm or data structure question. Maybe it's just NYC or maybe it's where I was applying.
It's likely an artifact of the jobs you're applying for but also consider that they're might be asking those questions now because in the past there were too many applicants who weren't qualified. It's only been fairly recently that front-end development has been taken more seriously as an engineering discipline.
That maybe used to be true, but these days that's absolute incorrect. A lot of non-Web developers are becoming "web developers", because such a large percentage of new software is written for the Web.