2) Not enough IPOs so lots of investor interest to deploy capital into something( (thus driving up the price, making it more attractive for startups)
3) We're near the end of a 7~10 year cycle where lots of private VC capital was deployed and needs to be returned
4) 500 private investor maximum SEC rule
VC companies themselves raise money from investors to create a fund, which is then used to invest in startups. Generally, funds are raised with a specific timeline pitch for returns to the investors - often 7-10 years. In order to return money to investors, the investments in the fund have to actually pay money back to the VC firm - the best way to do this is via IPO (although acquisition is also an option).
Due to overall market conditions, a glut of investment happened in the VC space 7-8 years ago (i.e. a bunch of funds were started), and those funds now need to get money back to the investors to prove a nice ROI, so there's a push to get the startups that were funded by the fund to exit one way or another.
Eh I have heard this for the last 5 years