It's soooo hard to tell who does or doesn't have a personality, and soooo hard to tell if what you see is real or a facade (didn't Lance look soooo cool when interviewed by Phil-Paul-Bob?).
In general, I feel that tough guys tend not to be very talkative. Endurance athletes are as tough as tough comes. Even in sports that puts bright lights on individuals and sets the stage for rivalries, clash of personalities (i.e. pre-fight build-up), for one Ali (huuuuge personality), you have dozens of Frazier, Foreman (the '70s George), Holyfield...add to that the reluctance to face a microphone when you've dropped school in 8th grade, that your grammar s**ks, and your vocabulary is 200 words max... add a country accent to that and you get '75 Bernard Thevenet. He was soooo bad

. BT was self-conscious, unlike Ribery, who keeps butchering the French language and doesn't care (know?) that people think that he's dumb.
The same debate took place about Tennis not too long ago. I would argue that if we focused more on knowing the players or riders, we would find out that they do have a personality. Fact is, most fans don't care. Unless it's an outrageous, bad boy, and/or over the top personality (Young Sagan, Nacer, Moscon, McEnroe, McGregor, remember Naz

?). And some are soooo fake: take off your shirt Ronaldo

!
The late Scarponi was a very funny guy, Valverde is reknown for his humour as well, I personally like Dumoulin saying things as he sees them, Phinney cracks me up, I don't need a diva screaming "show me the money" to like the sport.
The truth is: we don't know the majority of the riders, who they really are. And most pros like it this way I bet.