Here's a quote from 1760[1]:

“I well remember for many years it was not expected, nor was it thought possible [for porter] to be made fine and bright, and four and five months was deemed to be sufficient age for it to be drunk at. The improvement of transparency has since been added to it by means of more and better workmanship, better malt, better hops and the use of isinglass.”

[1] http://tempestinatankard.com/2013/11/21/of-isinglass-and-oth...

It goes back to 1722 which is very recent in beer terms. People where making beer 5,000 years ago.

Where did you get the 1722 number from? I've never found a good source on when the process started?

But still when people are talking about the beginning of "modern manufacture of crappy commercial beers" I think it's safe to assume that they are at the very least talking about brewing after the discovery of the role of yeast in brewing and the control that that offered to the process, which is still 100 years after the quote I gave was made.

I believe that it's likely to be too expensive for use in most crappy commercial beers, which are likely to be heavily filtered instead.