If you are going to refuse any offer don't waste their and your time. However if you might accept an offer you should prepare, since you want to know what you will be getting yourself into.
part of preparing is learning what the company does. Most of us work for a company the majority reading this have never heard of. you want to know what the potential company does so you can ask intelligent questions.
You might be misunderstanding what I mean by "prepare". I mean companies that expect you to have crammed algorithms/leet code/CS new grad before their interviews. Then if you don't, they treat you like you are a huge imposter/liar who cannot code.
I certainly am mentally prepared when I speak with a company and treat them professionally. I expect the same basically.
You need to go back and read what I wrote originally - I thought I was clearly stating that you shouldn't be cramming algorithms/leet code. That should be a waste of your time, and even when it isn't it is a bad sign if the company asks questions where such studying would be helpful (though sometimes that might your least bad option to take a job there anyway).
Prepare for an interview means look up the company. You often can figure out what style of interview they do and prepare to answer those questions. You often can figure out if there are concerns that you want to probe in your turn to ask them questions.
part of preparing is learning what the company does. Most of us work for a company the majority reading this have never heard of. you want to know what the potential company does so you can ask intelligent questions.