Also relevant is the nature of the product being advertised - in this case, it was a specific event - not a call to visit a website or even to visit a store that holds regular business hours. Clearly, this was a very effective way of drawing customers to the event but the lessons learned hardly apply to other businesses.
Lots of businesses can host events, IRL and online - a brick-and-mortar shop can host a sale or a meetup, an online business can host a webinar or a conference - in fact it's tough for me to think of a business that, by nature, could not host any type of event.
Whether it makes sense for them to advertise on Facebook - that'll be up to them to test, but events are a pretty tried and true marketing technique.
