I run a pilot lounge/flight school at a busy Los Angeles-area airport. I haven't seen much mention of service-oriented businesses such as mine -- but I personally think it's silly NOT to offer this courtesy.
I understand retail businesses (coffee shops, restaurants, pubs, etc) being reluctant, because they rely on high retail turnover -- but if you have service situations, especially where your customers may be waiting (say, car wash, mechanic, hairstylist, others) -- then why *not* provide this service for your patrons?
I've never had to make a cost analysis to justify a public hotspot -- it just seems like a nice thing to do.