For me it is the plugins, themes, icons etc. As soon as there is a plugin you can't live without, there's no way back. I can't remember which one it was for me but when I saw a co-worker using it I had to give VS Code another try.

Migrating over is easy too as you can import your shortcuts with "Sublime Text Keymap and Settings Importer"

All the plugins, The synced user configuration, github copilot, git integration (although I do use sublime merge a lot on the side), I used to work on a remote copy also via SSH (and I can't remember what plugin), there's just so much available out of vscode now, I feel like every new months it ships new features while sublime text didn't come up with an update in years.