Interesting thought. It would be complicated to pack this into something that you just purchase. Props integrates into Slack, Salesforce, Zendesk, etc.
Maybe we are not communicating the product well on the site.
Oh I'm sorry, I forgot that provider API's are magical, mythical beasts that must be tamed from an intermediary server, never from a client.
It's OK to say "we don't think enough people will pay enough for a one-time purchase to cover development costs". You don't have to invent some kind of technical reason for it to be a service.
But having said that, I cannot believe that companies would pay the amount you're asking for a service either.
Its about recognizing people doing great things in your org. It really has become a part of the culture in the companies that have been using it (and pay) for months now.