You've slightly oversimplified things; there are lots of different kinds of formal attire that end up getting called "suits" by people who prefer less-formal fashion.
If"business casual" is the upper limit of unsuited informality, does adding a blazer on top because the weather is cold suddenly turn you into a "suit", wearing a slobby improvised suit-and-slacks combo?
Honestly, it is a subjective question... and remember that some people might not even have the financial freedom to make all the fashion choices they want, and end up wearing from charity, precisely what the previous owners did not keep!
You've slightly oversimplified things; there are lots of different kinds of formal attire that end up getting called "suits" by people who prefer less-formal fashion.
If"business casual" is the upper limit of unsuited informality, does adding a blazer on top because the weather is cold suddenly turn you into a "suit", wearing a slobby improvised suit-and-slacks combo?
Honestly, it is a subjective question... and remember that some people might not even have the financial freedom to make all the fashion choices they want, and end up wearing from charity, precisely what the previous owners did not keep!