There should be a great diversity in user agents because there is great diversity in personal tastes.
One person's user agent might be another person's "software I would never use".
As a text-only web user I am continually amazed, thirty years in, that web developers and now their CDN service providers are _still_ making incorrect assumptions about what user agent I am using. They are wrong every single time. There is almost zero focus on rate limits but hyperfocus on user agent string or other headers. For most sites I send no user-agent header and this works fine. But when sites want certain headers this tells me the purpose is not "protecting" servers from being overloaded, it is "protecting" servers from web users who will not involuntarily provide commercially useful data/information so that access to them as ad targets can be sold for profit.
Choice of user agent should make no difference. The JSON I'm getting is the same regardless of what device or software I am using. I decide what I want to do with the JSON after I retrieve it.
Imagining how things could be different, there could be "commercial" user agents that people use for accessing their bank acconts online and for other commercial transactions. There could also be "non-commercial" user agents that people use to read HN. Unfortunately, the way things are now people are using commercial browsers for non-commercial web use and exposing themselves 24/7 to unecessary tracking and advertising.
Personally, I only use a commercial user agent infrequently. I'm not doing many commercial tranasctions over the web. Most times, I am using non-commercial user agents. I see no ads and can focus on the text.