Collecting rolls was a popular thing to do in the 60s and early 70s. These are plentiful for that reason.
Lots of BU rolls are unsearched, of course. Don't forget though that the seller might have had an entire bag (100 rolls) and if there were no nice coins in a sampling of them then he could be confident there were none in the rest. Very few people actually collected any coins made after 1964 and have no idea how bad most of the coins look. Availability of rolls is virtually nonexistent for dimes and quarters and is spotty for other denominations. Quality varies greatly from date to date and in some cases it will be virtually impossible to find any Gems in BU rolls even if you can find the BU rolls. Other dates are not too tough in rolls. Most Gems from the last 55 years come from mint sets but these tend to be tarnished now days. Roll coins are great where the mint set coins tend to be scratched ('80-D halfs for instance). There are always some unmarked coins that go into circulation but then they'll usually be poorly made. Rolls that can be easily opened and reclosed tend to be searched and even rolls that are hard to reclose (shotgun rolls) can be.
Yeah, this seller really didn’t seem like a coin collector, he only had two other items and they were miscellaneous a military back and some tools.