Socioeconomics play their part but that doesn’t answer the question as to why all women are looked down for seeking self-improvement.

and to your point, it can be said that the trend is now swinging in the opposite direction and can be seen either way. Very few people are forced to work all day outside in the sun anymore - most poor and middle class people work in indoor factory and office jobs and are subsequently paler than their wealthier peers. The entire rise of the tanned skin/skin darkening trend in the last hundred years is due to the desire to be seen as affluent enough to be able to afford the fiscal and time-associated expenses of vacations, travel and time off.

Doesn’t explain the crab-bucket mentality of why women pull other women down.