Modal verb “will” to describe a present situation

Question

I heard a phone conversation between a person wishing to buy theater tickets and a sales agent like the following:

“I want to buy two tickets for tonight’s show.”
“Certainly. I’ll need your credit card information.”

I believe just to say “I need your credit card information” makes perfect sense. What are the purposes/effects of using the modal verb “will” here?

Another scenario: let’s suppose the theatergoer asked the agent something for which the agent has no ready answer. In such a case, I know one would say something like:

“I’ll have to get back to you on that one.” Again, I believe the sentence is grammatically just fine without the “will." So, why do many people add the “will”?

I am interested in the nuances the use of “will” produces in the both cases.

Answer 1

Normally, in response to the request to purchase tickets, it would be enough to say

I need your credit card information.

But by adding will to the statement

I will need your credit card information

the vendor is taking the politeness level up a notch. The first statement is a trifle direct, even blunt. But the addition of the semi-conditional (which in effect says "If I am to comply with your request I will need your credit card information") makes it less of an I-vs.-you operation and more of a shared effort. It is simply softer to state it that way, and it suggests that you do mean to comply with the request and now only the details remain to be completed.

To illustrate what I'm talking about in a little more depth (or breadth, perhaps), let's make what I will call a "politeness ladder" and position the statement where I think it belongs in the hierarchy.

Roughly, from highest (most polite) to lowest (least polite):

Will you be paying by credit card?
How would you like to pay for this?
May I please have your credit card?
I will need your credit card information.
I need your credit card information.
Do you have a credit card?*
Give me your credit card.
Gimme your card.
Card? (Accompanied by an impatient gesture.)

^{* The politeness level of this statement depends on tone (as, to a degree, do they all). Stated in a crabby voice it could imply that the vendor doubts you have been extended credit at all.}