The difficulty bomb operates under the assumption that miners decide what code economic participants are running, rather than economic participants deciding for themselves. In reality, miners will mine whatever chain is most profitable and the most profitable chain is the one that economic participants use. If 99% of miners mine a chain that no economic participants use then that chain will have no value and the miners will cease mining of it in favor of some other chain that does have economic participants. Another way to put this is that miners will follow economic participants, not the other way around.

With the difficulty bomb removed, when Casper is released it will be up to economic participants to decide whether they want the features that Casper enables or not. If they do not want Casper, they are free to continue running unpatched clients and participating in the Ethereum network as it exists today. This freedom of choice is the cornerstone of DLTs and making it hard for people to make that choice (by creating an artificial pressure) does not work towards that goal of freedom of choice. If the development team is not confident that economic participants will want Casper, then they should re-evaluate their priorities rather than trying to force Casper onto users.

Personal Note: I think we will see almost all economic participants in Ethereum switch to PoS/Sharding without any extra pressure beyond client defaults.