It kind of depends on the details.

My company has offices that you can go to, but if you want to work remotely then it’s up to you to manage your environment.

The company already has offices. Why would they pay for more just because you don’t want to go to the offices.

There is a one time budget for hardware, such as a second monitor at home, we’ll have to see how that plays out with upgrades in a few years.

Because they don't have to pay for those offices anymore. If the company is allowing for remote work, they can also downsize those offices (subject to lease conditions), saving piles of money. (Commerical space is expensive!) If some of those savings aren't passed onto their employees, those employees will choose to move to a different company that has a more general WFH allowance, probably get a raise in the process, and work with a company that's just generally less obtuse to work at/for.

Once you factor in long contracts, the people who are desperate to go back to the office, and greater space requirements for proper social distancing - they pretty much do need to pay for those existing offices. Hopefully things will re-equilibriate, but I'd guess that will take another 2 years at least.

The cost of outfitting an employee with state-of-the-art equipment for their home office is at most a few months of commuter benefits. It's a comically small price to pay for employee happiness and productivity.

Employers that don't or aren't willing to pony up are going to be losers in the long run. Cheap is cheap.

The equipment is trivial and most tech professionals have it at this point or don’t really care. But you’re not going to get paid to move from your urban studio to an apartment with an office though some companies did pay for coworking spaces when there was no office for employees to commute to pre-pandemic.

Because you are saving pennies but losing dollars of productivity?

To be fair you could put your commuting costs into a piggybank and after a year you would likely have enough for a decent chair and monitor.