I think the problem is that they have a roadmap suggestion and haven’t bothered to work on the #1 thing on there
We just can't. The game is not in a state where it could support the fast chunkloading that would be needed for trains - it was clear to us that this will be one of the last and most optional features of all the things we want to do, no matter how many votes it gets. Votes alone don't decide what is implemented, they tell us what people think would be really cool. And trains would also be really cool for us. But there is no way to implement them at the moment, that is something you might see after the end of early access. I've already told our web developer that he might want to clarify what the roadmap is - a way to show what you find most cool to us and a way to show you what we plan to implement from us, not a vote on what we do next. I'm quite sure that will be part of the website relaunch that is planned for the future.