A professor I know through the EA community has been trying to hire a software engineer for their research, and they explained some privately about how this is tricky. The following are points I took away that might be useful to programmers considering job postings, people in academia looking to hire programmers, and people trying to understand why it's hard for EA projects to hire programmers despite there being a lot of them in EA.
Market rates for good programmers are much higher than universities are used to paying for anything. For example, a Senior Software Engineer at Google earns ~$350k, while the most this professor's university would be willing to pay, full-time, would be ~$100k.
That the money is coming from a grant doesn't resolve this: the university would still not let you pay a higher salary because you need to go through university HR and follow their approach to compensation.
Universities will let you pay more when doing temporary arrangements, for example, as an employee on a six-month term or as an independent contractor, because you're no longer implicitly paying partly in job security. This might allow them to get up to $180k-$270k without benefits, though still below market rates.
Depending on university rules, if you did want to hire someone full-time you might have to pick from a pool of internal candidates, even if those candidates weren't very good, or else make a strong case for why no internal candidate had the required skills. Since programmers earning university wages could be earning maybe three times as much if they were good enough to get hired in industry and wanted to switch, many of them are not great.
They showed me a public job description that had a very long list of required skills, and seemed to be targeting a more experienced person than the work called for. Not knowing the situation, I initially thought that this was due to a misunderstanding about what kind of candidate they actually needed, but it's how they convinced the university that they should be able to offer this high an hourly rate.
While this researcher hasn't done this, others have bypassed these restrictions by hiring someone for "40hr/wk" with an understanding that they're actually going to be working much less than that.
One effect of this is that if an EA academic project needs a full-time experienced software engineer, they will often need to hire an EA because they need someone who is willing to work for much less than they could get elsewhere. Even if the work seems like it could be done by a non-EA at market wages, academically affiliated projects won't be able to do that.
(The professor reviewed this post, and has asked to remain anonymous.)