Six months to land the right job holds for any job or field, remote or not. There's a lot of jobs available, but along with that you need to be picky - it can take some time to find a competitive, ideal option.
End of year 1: job A $100k, job B $60K
End of year 2: job A $200k, job B $180K
End of year 3: job A $300k, job B $300K
Of course if it's a startup, the odds are high that it would fold within three years. So unless it's a BigCo job that you are planning on sticking with... it's tough for me to make the argument that it's worth it to walk away from a decent but non-ideal offer. Employers know this and use this as leverage against you.
It's a problem because you end up with an employee who is now being paid below market rate. This is most effective against those who are not employed, but once they are employed they will be hearing from recruiters or start looking for the next job while still on the payroll. Because this company is unlikely to provide aggressive enough raises, their employees will be receptive to new offers. A year or two out, this employee gives 2 weeks notice. Was the win of saving the company a couple $10k worth it? Most likely not.
If employers have trouble both finding and retaining talent, then this is a mistake to leverage this against unemployed candidates. If you don't have this problem you soon will once recruiters discover a company full of underpaid but qualified candidates. People leaving is also a signal to current employees that better deals exist somewhere else.
Almost everyone worth working for is hiring constantly. Hence it's relatively straightforward to run a bunch of interview processes in parallel while still being quite picky about the offer you accept. In most cases, it's highly unlikely that a better option will materialize with additional time (in 99% of cases, it would have existed when you started).
And no, it isn't easy to do it in parallel because I'm almost always employed so my bandwidth is about one interview a month.