The Talmud states (Mishna, top of Niddah 13a):
כל היד המרבה לבדוק בנשים משובחת
The more bedikos (checks for menstruation) that a woman does, the better
This is brought in the Shulchan Aruch Yoreh Deah 184:1.
Sometime between then and now, it became prevalent (in my experience with anyone I have spoken to about the matter) for those teaching the laws of family purity to instruct that women should not do any additional checks. One reason given is that since our bedikos today, due to our uncertainty and lack of proficiency, only produce doubtful or questionable results, they do not fulfill this praiseworthy practice (Igros Moshe Y.D. 4, pg. 201). Another reason is that women today are more sensitive, and doing increased checks causes unnecessary bleeding, which is painful and causes more halachic problems (citation needed).
My question is, when did this begin to change, and when did it become prevalent?
(Bonus brownie points for sources to the second reason)