You can use a conventional vacuum if it has enough suction (most of these dust mite vacuums are rated at 13 kPa, a sweet spot for extraction without damaging fabric), and if you don’t mind using the same vacuum attachment on other surfaces. These also have rotating polyurethane fins that go close to the surface which helps in agitation — most vacuum attachments have plastic brushes which I suppose will do the job but possibly slightly less effectively.
It’s not a mattress vacuum so much as a dust mite vacuum that can be used on couches, fabric chairs etc. It’s also handheld and is specialized for the job, so it’s more ergonomic to hold.
The UV I can’t really vouch for but can’t hurt. I personally would not run a conventional vacuum on my mattress because I use the same vacuum on less hygienic surfaces, but if you have a dedicated attachment why not — I feel it would be less effective (because in my experience, the suction is often diminished when you use an attachment) but have no data. If you have a high end vacuum this is less of a factor, but most low end vacuums like Hoovers aren’t designed to deliver full suction with attachments.
I’m happy with my purchase because I feel that given it’s small size, I’m more likely to vacuum more frequently. I’m less likely to want to bust out the big vacuum.