This would make a great little lore item in some RPG to explain why there’s a spell list.
‘We have literal magic that can raise the dead and move us across the world in the blink of an eye. Why the fuck am I having to do dishes by hand?’
‘Because no one actually knows how the spells we have work. We just have these spells left over from when they did, and ‘clean dishes’ isn’t one of them.’
The standard point is most around how big that ‘partly’ is, and how attached a project can become to that part. If a project has, for easy math, a $10M bankroll and $5M comes from, say, Goog or MS, the project can face a moment where the corporation comes and says, ‘we don’t like that you’ve implemented this feature that interferes with our control of users. We’re pulling our funding unless you remove it.’ (more realistically, ‘we see you have allocated some dev time to this feature request we don’t like. Cancel it before the public can demand it.’) If that happens, you have to have a project lead with some real rectitude to say, ‘okay,’ and just cut their budget in half. The more diversely sourced a FOSS project’s funding is, the harder it is to control, and vice versa.