Nope, not at all! just many people may have issues doing them (showing their face due to their profession, shyness or any number of things) or just don't do well speaking in front of crowds (aka the internet) so just do written a lot more often.

As well, consider that video reviews also help people see EXACTLY how big a toy is in real life which text reviews and the site don't always really show down to a science so they are helpful for that. As long as you give just as much info as you would for a text review and your full hearted opinion on it, video reviews are just as valuable as text reviews.