Why people use 'come across as' here?
In American TV show 'Office' Season 2 Episode 1, Jim tried to persude Michael not to use the same party jokes every year. Jim said to Michael, 'I think if you use the same jokes, it just comes across as lazy'.
What did he mean?
It means "appears to be". See the definition at:
Merriam-Webster Dictionary: come across
This is a situation where person 1's actions make other people guess information about person 1's personality. It is information about what are like inside your head and your heart. (The impression that comes across may, or may not, be reliable.)
Coming across to other people in a certain way is not always intentional, but can be planned. For example: if you want to come across as professional at an office job interview, wear formal clothes. How you come across can be more about how you say or do something than what you say or do.
