I would say it's quite similar to having a touch device with an integrated pen holder where pen disappears in the device (so it can't fall out) and not.

It is a "gimmick", but if you are frequently shuffling your laptop around, having a bag clear of dongles and "floating" stuff is a world of difference.

I mean, even thinness in laptops is a gimmick (it's actually the first thing I'd do away with to get maintainability, battery life and better cooling/performance/noise — fanless, anyone?), but it sells like hot cakes.