I assume the preflop raise is done for multiple reasons but a player who raises sometimes will offer more information about their range than a person who never raises preflop. For giving up this bit of preflop information there must be a bigger tradeoff gain to the raise.
Is the goal of the raise to eliminate weaker hands? Someone might call with 9-T off but may fold to a raise.
Is the goal of the raise to build the pot? If my standard post flop bet is 1/2pot, then I’d rather $100 in the pot, opposed to $40, when I hit the flop.
Or is there another reason?

Player A calls 20%, folds 80%.
Player B raises 20%, folds 80%.

Why do you think player B offers more information than player A?

Raising does a few things:

- Takes the blinds
- Builds a pot with a good hand
- Makes the other player fold their share of the equity

Having a strat where you sometimes but not always raise might arguably provide more information about the strength of your hand than someone who never raises. However that is not a good enough reason to not raise.

Providing information as a result of playing good poker isn't a mistake. Like if you raise UTG on a 9 handed table, you likely have a good hand, which narrows your range. That doesn't mean you should decide to fold 100% UTG going forward or start raising garbage in order to deny your opponents insight into your range.

If one player A only calls and never raises, and player B sometimes calls and sometimes raises, then player B is sharing more information about the preflop ranges. Don’t you agree? So there must be a larger benefit to raising if it’s also giving away some information. I’m asking about which gain/gains outweigh this sharing of information. And asking what is the goal of the preflop raise ?

Not necessarily, unless the decision on raise or call is simply based on strength of hand. Then yes, if somebody raises AA and nothing else, he gives away information. And if somebody calls AA and nothing else, he gives away information, too.

WereBeer already listed the reasons to raise. But just to add one more simple example: Player A has AA and knows that player B will call preflop, no matter what. What should player A do, fold or call or raise all-in?

One of the things that a player should never do is alter their bet sizing based on hand strength. Bet sizing should be based on external factors like position, game context, and frequency. If done correctly, a preflop raise should give your opponents no additonal information other than 'This hand is in his range of hands he will play'. And, if constructed properly, that range should include an appropriate mix of value hands, drawing hands, and bluffs.

Preflop raises are done because they force other players to react to your play, which both narrows their range, elevates yours, and draws out information from them.

Postflop that's not true. It's fairly common if you split your range in multiple bet sizings to bet more polarized with the top of your range, as long as you're properly balanced it's not a problem.
Theoretically I guess you could do that preflop too but it would be really impractical and most likely counterproductive.

It's basically ^this^.

Experience shows that raising makes more money than limping or calling, since it gives you an additional way to win (because your raise gives other players have the opportunity to fold). The BB never folds to a limp.