I guess that's very country-specific. In my country (Uruguay), as a professional, I'm EXPECTED to wear a suit, and I own far more than 3 (it helps that they're about U$ 100 each as opposed to whatever price they are in the US).
He says that you eventually want to own three suits. Once you start wearing suits for different occasions, it's pretty obvious, at least IMHO.
A black suit is good for formal use. Church-business, meetings with executives etc. You're conveying the message that you're dead-serious. A charcoal suit works well, also, as mentioned in another comment.
A lighter suit, maybe grey with a very light pattern, no color, goes well for anything non-dead-serious. The message is that you respect and take whomever you're with seriously. Lower level meetings, fancy restaurants, conferences. A black suit don't go well here, because the situation just isn't dead serious.
The third suit is for when you're used to wearing suits and like it (if you don't like it, don't go there) - something more playful, something like a color pin-stripe is popular. Generally not for business-use, but for going out. If you show up at a post-conference cocktail reception in a suit like that it says "let's enjoy ourselves" and shows another side of you.
Upvoted for your mention of dressing to signal your respect for others. It seems many geeks rarely think of this. To many geeks I have known, their down-dressing is about their comfort and desire to buck mainstream culture. That's fine, but it would be nice if they realized that dressing nice at work or out with friends can also mean you think those around you were worth some effort. After all, you don't have to look at yourself all day, but everybody else does.
I respect you enough to think you are a person who can find more useful signals of respect than the ability to memorise and abide by arbitrary rules laid out by the unseen gods of menswear. ;)
Then you are a better person than I. If someone speaks too familiarly, acts too familiarly, or dresses too familiarly in a serious or business setting, I will not be thinking that he respects me enough to think that I am a person who can find more useful signals of respect than the ability to memorise and abide by arbitrary rules laid out of the unseen gods of grammar, social conventions, or menswear. I will be thinking that he has no respect.
It's not just memorizing. That's the problem. If it was memorizing, my iPhone could memorize it for me. You have to think about fashion. And I don't want to. And I don't want other people to invade my mind and dictate part of its contents.
If I dress up for you, I'm announcing that I believe you can be manipulated by a simple costume change. I'm not above using that tactic but it certainly isn't out of respect.
1) you don't want to look dead-serious. Most people like business interactions to be relaxed.
2) most formal matters are conducted in the daytime. Daytime environments--outdoors, fluorescently lit offices, places with the windows open--will be brightly lit and comparatively low contrast. In these environments, black sticks out a mile away. There's a reason black tie is only considered appropriate during the evening, when street lights are on and interiors tend to use more relaxed lighting.
3) there is a rule in America that black suits are only appropriate for very somber occasions. Not everyone knows this rule, but some do.
4) cheap black fabric stands out a mile away. Cheap fabric of any color, not so much.
Get a dark ("charcoal") gray suit instead of a black one. Charcoal gray is the world's most boring color, making it perfect for interviews, presentations, important business, etc.
I bought a nice, black suit for formal use. I was taking the advice of a good friend of mine who I brought along to help me. I took her advice because she is a woman ten years older than me with a background in textile engineering. Her reason for why I should pick black was "You look better in it."
What's wrong with 3 houses? 1 to live in, 1 for impressing and 1 for working.
Of course, you outsource the impressing one to whichever social building is appropriate for the event and outsource the working one to your office, but still.
Maybe you could have a daily driver, and either hire a van as needed, and have a weekend car or hire one as needed, or own or hire both or indeed all three.
That's like asking me to own three cars.