Press was removed a bit after the 1972 Olympics for two main reasons -
1) Time. Weightlifting is a boring sport most of the time, as the Olympics got more commercialized, there were mumblings about the time meets/events take, and to shorten them to make more room for other sports. Originally the modern era of Olympic lifts were 3 lifts - 1 handed snatch and C/J, and regular Clean and Jerk, then 5 lifts - One handed snatch, one handed C/J, Clean and Jerk, O, Press, and Snatch.
That was the original reason for the knurling in the middle of Olympic bars. The one handed lifts were gone after the 1924 games for much the same reasons.
2) The lay back in the Olympic Press post WWII, particularly advanced by the Eastern Bloc countries was a large sticking point among countries and judges. So in 1972, with the push to shorten events, and the increasingly hard to judge nature of the press, it was decided that they'd just get rid of it.
Post WWII lay back pressing method -
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