Long-term-stable color photo processing didn't become widely available until the late 1970s-early 1980s.

So if you were an artist and interested in building and maintaining a permanent portfolio, B&W was pretty much your only option.

In the 1970s color film/development/print cost significantly more than black and white.

Shooting in b&w was common, because it was much cheaper. But of course, he could've chosen it or aesthetic reasons.

You can process and print B&W yourself. Color needs to go to a lab.

B&W is also standard for street and art photography.

You're gonna argue this _now_?

"The past is stupid"

Could you please elaborate your thought process here? For example, are you claiming the author was using obsolete tech for one reason or another? Or making a pretentious artistic choice? Or do you think these were taken in an earlier period, then misatributed as being from the 1970s?