2 ways are woofer/tweeter. That is all that is needed to produce the full audible spectrum. 3, 4, 5 ways (etc) simply add more tweeters.
There is nothing about these mulit-tweeter speakers that makes them better than a standard 2 way, and in most cases they are much worse. Unfortunately, many manufacturers have recognized a lot of uninformed consumers live by the principle that more is better, so they automatically lean toward the 3 4 and 5 ways thinking 4 tweeters on a small speaker must be better than 1.
Look at a good car audio retail website -- sonicelectronix.com for example.
Go to their 6x9 speakers and sort them from high price to low. You'll see that above $100 there are mainly 2 ways, with a few 3 ways and two 4 ways. Below $100 there are a few 2 ways, several 3 ways, and a few 4 and 5 ways. There's even an 8 way, it's $35.
I don't think that pattern is a coincidence.