Who’s to say that other people’s preferences are more important than their own,

Because communication is about getting your ideas and opinions into other people's minds. I may prefer to write in swahili, but my audience prefers English.

particularly given that this particular preference is shared by millions of other people.

Over particular mediums for particular topics, yes the all lowercase preference may dominate. ALL CAPS FOR SHOUTING and miXeD CaPs FoR cRAzY provide excellent emphasis. But history shows that capitalization is an advantage. It was invented during the printing press and stayed as convention.

Here's some more discussion

Having tried to learn a language (Bengali) that does not use capitals, I can attest to their use. If you're starting out, how do you tell a name from another noun? Are you talking about chandra (the moon) or Chandra (the common surname)? There are so many cases in every language where common and proper nouns overlap, and having capitalization is very helpful.