Do I really need to backup MacbookPro during keyboard replacement/repair?

YES.

If there is a problem that requires your mainboard to be replaced or even re-imaged, your boot disk will be erased.

You need a disk-based backup of ALL your files and photos. They could disappear for no good reason at any moment.

Time machine backup software is provided, free. All you need to provide is a drive to store things on. After the first full backup, it runs at low priority in the background, without slowing your important work.

Back up your Mac with Time Machine - Apple Support

.

If there’s nothing on the Mac you care about, no. Otherwise, yes.

But your question can be inferred to mean there are no regular backups, which means the data here is one drop or one loss or one theft or one fire or one dunking away from catastrophic loss.

We get to see far too many of the “Help Me!” postings around here. Far too many. When most or all of that data is now irrevocably gone. Some of that data usually being irreplaceable, too.

Yes, backups are important.

Backups before repairs? Definitely yes.