Registering is a wise safety precaution.
In a very small number of cases, manufacturers may identify problems with an appliance once the product has been in use for some time. They then need to contact you to get the fault corrected as quickly as possible. Normally a quick in-home fix by a qualified technician will banish any risk.
It can be very difficult to trace customers as they often do not provide contact details when they buy a product. So as a consumer, it is important that you take the responsibility to let manufacturers know that you own the appliance and ensure that they can get in touch directly should they need to.
Registering can also save you money by entitling you to an extended warranty or guarantee period.