Late to Mass

Not us...
This couple, probably in their 60s?70s?  Every single 5pm Mass...late.  Blatantly.  Middle of the Gospel Reading, late.  Like, Mass is halfway over, late.  I don't understand it!  They don't have small children to dress.  They don't seem handicapped at all.  They obviously can figure out after hundreds of times coming in late that 5pm Mass does not start at 525pm. 
I have little room to complain...we don't always make it to Mass...sometimes I have an excuse.  But, whem we go, we get there on time...I've been late once in 32 years, 5 minutes late.  We don't even miss going very often, I'm jut saying, sometimes we do miss.
Come on, people!  It hurts me to see 2 capable adults walk into Mass at 525 each week...leave earlier!