Yeah they do. Actually they get turned into cash after each coupon payment and at maturity. But it takes time (as long as 30 years for some bonds) to turn the bonds back into cash. So this has the effect of taking liquidity out of the economy, while not making anyone any poorer.

When you take out liquidity, people's money are now locked in bonds and they can't buy anything else with that money unless they sell the bond. So this has the effect of reducing demand for other financial assets like stocks, real estates, cryptocurrency, etc in the short term.

The hope is that in the long run, the economy will grow enough to be able to support the eventual increase in the money as the bonds mature.