Why do people care that a politician earned money giving speeches?

I don’t understand why it’s a big deal that a political candidate earned money making a speech. I keep hearing about Hillary Clinton making money giving speeches to Wall Street, and a call for her to release transcripts from the speeches. I can see people being interested in the transcripts, but I don’t understand looking down on a candidate for working and earning money, especially when they are no longer in office. I can see an argument against while they are still in office.