That's cool I guess, but it's easy enough to just spin up your own instance that you fully control in like ten minutes. Can't see myself using this or recommending it to employers. Maybe I'm missing the point?
While debatable, It's often cheaper to pay someone to host than to do it yourself. Imagine a 1 sysadmin small devshop that doesn't want to pay for 24/7 on call support but does have devs working in different time zones. Or a big enterprise that needs support (perhaps someone to blame). Joke about corporate culture if you want, but often it's less stressful to blame a vendor than an employee or the internal culture. It may take 10 minutes to set up. Hours a month to maintain. Weeks to get permission to install it. Time to hire support sysadmin staff. Time to explain why kubernetes/simple vm/heroku/shiny new thing would make hosting it easier.
Why not github? Perhaps the person or org just likes open source. Distrusts Microsoft. Wants the option to self host as a bail out strategy. Or just dislikes github. Competition is great.
This argument applies to most open source apps with hosting options. I'm a fan of this model.