A ban would make it illegal to hold, trade in, mine, stake, etc.
It would still be possible to to do all these things, but it would be illegal. It won't be possible for governments to actually stop all activity, just like child pornography laws don't prevent the stuff from getting produced and traded (note: I am in no way equating these things in any way). But it would critically damage the value of the assets.
This is a race of crypto getting too big to fail. The further adoption is progressing, the less likely an outright ban will be. In democracies there are also legal/constitutional issues to consider. The Supreme Court of India has struck down a crypto ban before.
Also, legislators tend to be well-connected and much wealthier than the average citizen. They are increasingly likely to invest some of their own fortunes in cryptocurrencies and/or use crypto tools like DeFi. They will be accutely aware that they would damage their own portfolios.
Several people in the Biden administration, e.g. nominee for the SEC chairmanship Gary Gensler, are crypto-experts and optimists. If they do not destroy the market during the next four years it might be too big to fail already.