It's closer in spirit to buying a pack of smokes, it's easy to just grab one on the way somewhere, less of an issue if you lose it or have to toss it(like at some concert venues), easier to give to your friends, and generally they are much smaller, so easier to conceal.
Maybe I've just been lucking out, but every concert venue I've been to recently has let me in with my vape. I usually tell the security person I have it on me, and then they tell me it's fine and pass me through. You're right though, it would suck to have to toss it.
I don't agree with the "smaller" part though. Most of the disposable units I see are thicker and wider than my refillable one, since they need to be long-lasting as a value proposition. I think the main draw is probably pure convenience.
Personally I think they're useful for one thing and one thing only, a gig/night out. When you don't want to have some kind of battery pack to recharge your vape so you have a couple disposables in your pocket, and if you lose it, shrug, it cost a couple quid.
Someone said it's an easy thing to get and "flavourful". There's plenty of cheap expensive vapes... I've seen coworkers with £250 on the unit itself and they have to clean it and replace coils? I can understand someone wanting a care free alternative" that works".
Not for me, just answering your question based on what I was told.
My rig cost me $50, a month's worth of juice and coils is $40.
I see the big expensive rigs and I don't want to spend that much on something I'm hoping to use for a couple years, max. Plus if I lose it I'm out a ton.
In my experience most of the non-disposable options are either super bulky or just shitty build quality. Pods that leak, or burn out super quickly. Vapes that just stop working or break super quickly. Incredible inconsistency in where/what pods are available.
None of these are insurmountable problems, but as of right now most companies seem uninterested in making a better product.