No need to build your entire startup on Slack but a solid integration can drive serious initial revenue for your startup especially if you do not get a lot of direct traffic. "One click install" is what helped Woocommerce and others get massive growth on the back of Wordpress through top exposure in the plugin directory.
Slack is still very much at the bottom of the growth curve. I have seen electrical contractors who need a way to chat with onsite workers at various projects switch from using WhatsApp/SMS to Slack. If one click job scheduling apps start appearing in the Slack App Store they will be quickly adopted by these businesses. I would be surprised if Slack or something like it has not completely wiped out internal email in 5 years.
Slack is still very much at the bottom of the growth curve. I have seen electrical contractors who need a way to chat with onsite workers at various projects switch from using WhatsApp/SMS to Slack. If one click job scheduling apps start appearing in the Slack App Store they will be quickly adopted by these businesses. I would be surprised if Slack or something like it has not completely wiped out internal email in 5 years.