Bandwagon effect

Tendency to follow the crowd. Adopting behaviours, practices, attitudes, beliefs only because others are doing it.

This can happen because individuals prefer to conform, or because individuals derive information from others.
Much of the influence of the bandwagon effect comes from the desire to 'fit in' with peers; by making similar selections as other people, this is seen as a way to gain access to a particular social group.
Bandwagoning serves as a mental shortcut.
Fear of missing out.
Being on the 'winning side'.