It isn't necessary.
In this case, we are using 'help' as a causative verb. Causative verbs, such as 'make' and 'let', can be followed by a bare infinitive (without 'to').
'Help' can be either a causative or a non-causative verb : you can either 'help someone to do' something, or you can 'help someone do' something. There is no difference in meaning.