Perhaps I'm misreading your question, are you asking why they invest in fonts?
If so, the answer is that fonts are a major underpinning of how an organization or a product is presented to the world.
To make an analogy that the hn crowd might understand, the value of a typeface for a design system is like the value a cryptographic primitive or a library like openssl to a functioning security system.
Nobody (aside from designers and typographers) will think "oh wow that font is so great they must have invested a lot into it", but it underlies every written visual interaction between the brand/product/company and its audience.
That said, are there many other fonts available that fall into the appropriate style, usage, licensing terms, etc that GitHub need? Perhaps. But uniqueness is a value in itself, and having a decision about a set of fonts that the company uses is a pretty important thing.
It's like the 3 spaces or 4 spaces vs tabs discussion. Some people use one, other people use another. But in a company, having an approved typeface that is recognized internally as the typeface to use (of course, you can have different typefaces for different scenarios/uses) - is just as important as determining which one to use.
In other words, marketing budget big and needed to be used up or else shrunk next fiscal cycle.
/s
Realistically, this is probably very cost efficient as it’s a relatively low effort project compared to a fully fledged feature, and something that can make someone say “hey, that y reminds me of GitHub”.
Fine, but are there any good reasons to spend resources on fonts?
Maybe if they spent less resources on achievements, fonts, etc. and more on reliability they could improve their downtime, which seems to be happening more and more often.
The time/investment they spent on their two brand identity typefaces is one side of the equation, the other side is the many, many minutes spent on font decisions in each and every little project in their company if employees are allowed (or maybe even encouraged, it can be quite motivating) to dabble a bit in "visual project identity". And on font licencing awareness training, because those engineer doodles will likely be public. And a Microsoft subsidiary will be an extremely juicy target for licence vultures, github simply can't afford any mistakes in that field.
This is where the wide parameterization of the fonts comes into play: "use one of those two fonts, feel free to go wild with the parameters" is much more likely to actually be followed than "use one of those n fonts, no exceptions", for almost any value of n. And better for morale as well.
You're saying it's better for morale, but do you have any proof? My personal experience says the contrary, the company I work at did the same (albeit it's much smaller than GitHub) and I asked some coworkers what they thought about it, about three of them considered it was a waste of resources, I only remember one saying it was OK, so overall morale went down.
Standards make sense but it how many san serif fonts do we really need as a species? It was someone’s job here to set out and reinvent the wheel, and that seems like a waste of effort to me.
If so, the answer is that fonts are a major underpinning of how an organization or a product is presented to the world.
To make an analogy that the hn crowd might understand, the value of a typeface for a design system is like the value a cryptographic primitive or a library like openssl to a functioning security system.
Nobody (aside from designers and typographers) will think "oh wow that font is so great they must have invested a lot into it", but it underlies every written visual interaction between the brand/product/company and its audience.
That said, are there many other fonts available that fall into the appropriate style, usage, licensing terms, etc that GitHub need? Perhaps. But uniqueness is a value in itself, and having a decision about a set of fonts that the company uses is a pretty important thing.
It's like the 3 spaces or 4 spaces vs tabs discussion. Some people use one, other people use another. But in a company, having an approved typeface that is recognized internally as the typeface to use (of course, you can have different typefaces for different scenarios/uses) - is just as important as determining which one to use.