I left Trello for Kanboard so I might not be the best person to ask lol.
I imagine one big reason might be if a workplace has used Trello for awhile. Switching costs are very high for a tool like that if it’s use actively. No one wants to pause an ongoing project, migrate tasks out of one tool into another unfamiliar tool, and start the project back up, slowed down as people learn the new tool. Trello was pretty popular for awhile and was the “default” way to do kanban-like stuff at many companies, so I can imagine many people got locked into it back then and now aren’t in a great position to switch away. That’s just a guess though.
I left Trello and at first I was a bit disappointed with the learning curve of kanboard but now I’m very glad I switched.
I think a big barrier for others would be installation. If I didn’t have the hosting account already and didn’t have the convenience of Softilicious, I probably
would not be trying open source self hosted alternatives.
Absolutely, both. Also, being held personally responsible for the tool. I would say this is #1.
Users tend to be non-technical. You are introducing the ability to be held responsible for them, where-as no one will hold Trello responsible for mistakes.
When introducing and encouraging Kanboard as tool, make it available as a tool which is not dependant on you.