Two possible reasons are:
1.Situation following crisis
If your home is damaged by fire or flood, you may need to move out temporarily so that we can repair the damage.
2. Maintenance or repairs
We need to make sure your home is safe and up to the required standard.
Substantial work is usually completed before you move into your home, but sometimes work needs to be done while you are living there, especially if you have been a tenant for many years.