I think the main reason is that appearing “pro se” has the risk of a mistake being made in filing or a response and the case being dismissed. The filing fee is $400 USD, and most of the paperwork is received and sent through the legal system you have to pay for (or may need to be a lawyer?). From your end it might need to be paper and mail for filing the case, receiving approved summons, getting summons approved, sending the summons to the individuals, paying for a process server if you want a summons received notice. After all of that (barriers that are nothing to a lawyer but might prove very frustrating for a normal person without access) it takes up to two months for them to look at it. It’s very possible they may choose to fight it after seeing self representation, especially if they think you aren’t able to travel to appear in court. They could file motion to dismiss or transfer the location, file extensions, all of which are just delays or run the risk of an incorrect response with docket filing or summons.
It’s also possible they just resolve it as normal, because to be honest they hardly ever do anything with a Writ of Mandamus, it’s just filed and then they fix the issue before the 60 days.
It just isn’t as simple as writing the court letter and submitting it. I think you could do it, I considered it myself, I just realized that there are many artificial hurdles that are difficult to find out about in advance, and some of them give you less than 24 hours to resolve before automatic dismissal.
If you haven’t already, check out pacermonitor, look up a name that appears on many WoM like Blinken, set the case type to Immigration- Other immigration actions and have a look at them. You can pay to see more than the 20ish cases a day, and you can pay to see some of the documents filed.
Also RE: lawyers making money, I don’t hate that they’re making money, it seems like a great gig! It even crossed my mind to start an immigration firm and hire a lawyer as an employee to file them because you could churn these out for cheaper than everyone and still be making money hand over fist. I hate that I’ve seen them encourage people to file when they don’t have standing. In my opinion, encouraging a lawsuit for $5k or more when you know legally there is no standing, have previous dismissals stating so, and you’re recommending a lawsuit to everyone complaining without knowing any details of the case- that’s the kind of slime I’m complaining about.