Why does the startup list keep adding apps I removed?

First, check whether the entry has actually switched back to Enabled, or is simply still listed as Disabled. Turning off a startup app doesn’t remove it from the list—that part is normal.

If it really re-enables itself, open the app’s own settings and turn off options such as Launch at startup or Start with Windows. Some apps or their updaters recreate startup entries, especially after an update.

If the app launches while its startup entry stays disabled, it may use another route, such as a scheduled task or Windows’ Automatically save my restartable apps… option under Settings > Accounts > Sign-in options.

For persistent cases, Microsoft’s Autoruns can show additional launch points. Search for the app or publisher and uncheck only entries you can identify; don’t delete unfamiliar registry entries. If you no longer need the app, uninstalling it is more reliable than repeatedly disabling its startup entry.