Letting them think there will be enough food and an open bar and then not providing the stated drinks and having far from enough food is what makes it bad hosting. A toned-down event can be planned for by the people attending--they'll know to bring extra cash to pay for a meal for their child or whatever, or will plan to make something else to eat once they get home. But an event that is lied about cannot be prepared for.
There are limits to this, I find.
Having a low key dinner with casual food - ordering in pizza and having soft drinks, or doing a back yard BBQ, say, is fine. Having a dinner at a low end restaurant , or having a restricted menu and drink choices rather than free choice of anything and as much as they want is fine.
Having an event that doesn't cover a meal hour is fine - make it an after dinner coffee and dessert, or mid afternoon tea and snacks.
If you're having a get-together of a group of friends or a family reunion, then you can always talk to others and share the burden of hosting - split the costs, make it a potluck, etc. But then you do have to give others a say in what you do and how much you spend - you can't just send them a bill for what you decide.
But if you're having an event over a meal time, you need to produce quantities of food appropriate to the time of day. If you're having a 5-9 pm party, and serve chips and pop, thinking that people can always go out to a restaurant after the party or eat dinner at 4pm so they don't get hungry during the party you've crossed a line into poor hospitality even if you warn people that you're not feeding them.
If you're telling people to bring money to buy their own beverages, or to buy their kid's meal, I think you've also crossed a line - you're not actually hosting, you're providing an opportunity for people to pay for themselves without giving them a say in what the event is.