Add devices without restarting home assistant

When I need e.g. a new input_boolean, I have to add it to my configuration file and then restart home assistant. Why is this so? Is there something I don´t know about?
I know that adding like esphome and zwave can add sensors, switches and so on without restarting, so why can´t I? Of course, I have the same problem with mqtt sensors, switches etc.

Because HA loads the data from your config file at startup rather than dynamically reading it during operation

The ability to add entities at runtime is slowly but continuously being added for more and more components and platforms. So, to stay with your input_boolean example: in the best case you only need to find a volunteer who builds a config flow for this which would then allow you to add and remove input_booleans at runtime.

Thanks guys. That´s about as I thought it would be.
Adding/removing input_boolean aren´t that important.
A UI for configuring MQTT devices would be very welcome.
I can live very well with this, of course. My reluctance/hesitation concerning HA restarts have mainly been based upon my previous bad experiences with zwave restarts and latency problems. They´re slowly going away.
My only concern will then be that I risk restarting HA e.g. in the middle of a timer period so that the light in my bathroom will stay on until the next time someone enters and leaves it. But I can live with that too!

There is way around this. See Guest Mode with some flexibility. I don’t claim to have done anything clever but it does solve your problem.