The government isn't exactly rushing to 4th doses. They could authorize it for under 50s right now, but there's little evidence that it makes a significant difference, so they haven't.
Also note that we still don't have vaccines for kids under 5.
If the government wanted to line the pockets of pharma more, there's not a lot stopping them. So it's hard to take blanket statements about this seriously. I'm not denying that this has happened in the past, just that it's a lot more complicated than any single conspiracy theory.
There's probably more money to be made by treating lots of Covid patients in the hospital. Drugs, equipment, exotic treatments, doctor bills. Vaccines are less profitable. Get outta here with your conspiracy theories.