I think endorsements mean two things usually:

1.) Your good at gaming the system. In college, it wasn't unusual to see entire classes sit down, connect, and endorse for everything you had "skills" added for. Bam, hundred of endorsements.

2.) Your connected with people who are a combo of being a bit clueless and want to be nice. It prompts you to endorse people all the time. Like my sibling comment's anecdote, you often get endorsed for random things from random people who have no clue what the skill is, but want to be nice.