What makes you think VHS are so sturdy themselves? Many tapes I borrowed were dirty so you could hardly see a thing, or washed out because they've been used so much. And sometimes they twist or mangle or snap. Not to mention the fact that they slowly degrade even when you're not using them anyway.
And as for other magnetic storage like flopticals or hard drives, forget it. Too expensive. Maybe in 2020 when the manufacture gets cheaper (if we don't get an energy crisis). Same goes for flash.
DVD happened to be the only affordable and suitable technology around that fitted what they wanted - medium res compressed digital. They could have put the same stuff on a magnetic tape and sold that, even, but really, magnetic tape is on its way out.