Let’s explain this a slightly different way. My barbarian has just found out that his detested cousin has taken advantage of his absence to usurp his position. He enters a bar looking to let off steam.
The DM briefly describes the bar. Large mirror, wood panelling, halfling barman on a stepstool.
I, as player, have an image in my mind’s eye as to what this bar looks like. The image is more detailed than the description: that’s how humans work, and without that RPGs probably wouldn’t be possible.
In game:
My barbarian is spoiling for a fight. He walks up to the big guy at a table with friends and rudely knocks off his hat.
The DM didn’t establish that there was a big guy at a table with friends. He didn’t establish that he was wearing a hat to knock off.
The alternative, which would break immersion for some posters, would be to interrupt their action declaration.
1. Ok, is there anyone in the bar?
2. What does he look like?
3. Um, does he have a hat or something I can knock off?