You can learn negotiating by working on people skills generally. The biggest takeaway from my college class on Negotiating and Conflict Management was that both parties will decide the other is "being difficult" when they are having trouble coming to terms, but the actual root cause of the problem is usually that there is a narrow range in which you can both benefit from the transaction.
So, learn to talk to people around you and ask why rather than accuse.
Also look up the term BATNA -- Best Alternative To A Negotiated Agreement. If you understand what your options are if you can't get cooperation, that helps define "how low should you go?" The answer: No lower than your BATNA. If they can't improve on that scenario, they can't add any value. It's not a deal you should make.
Also, information is power. Research the problem space so you know what your options are.
Last: Value is found in your differences, not your similarities.
Ideally, you want someone saying "Man, I hate oranges. I would happily trade my oranges for your apples!" where you hate "apples." Win-win. You both feel like it cost "nothing" and was all upside.
I also suggested some good negotiating books in a different comment.
That said the question is do you want to get good at negotiation not 'are you a saint who thinks they would never waste someone's time' (which I dispute per my other thoughts in this comment to begin with).
Guess what? I get a ton of tire kickers for my services that are referred to me. In some cases I know right off the bat that these people can't afford what I do and are 'wasting my time'. I still handle them with courtesy and take my time (knowing that I am wasting it) to help them. In some cases I enjoy doing so and in other cases I know they will then refer others to me. Many times these are people that have been referred to me (actually most times). I don't discourage it either. I know overall it's a good thing not a bad thing.
Auto dealers spend a ton of time to get people into the showroom. Advertising to sell cars. But did it ever occur to you that just like a restaurant [1] that is busy they might actually want the foot traffic because it makes things look popular and encourages others to buy (who are there)? Ever occur to you that it's good training for the sales person (who runs deals by the sales manager)?
[1] Restaurants will often trade at less than menu rates to have the restaurant be busy (even lose on diners) so that others (that are paying full price) will feel better about eating in a non empty place.
There's a difference between tire kickers who are curious and maybe have some low level of interest, like cars, etc. They don't even take much time, because they aren't going to the negotiation stage that would be so time consuming and yet be required for what you are advocating. You're advocating for a callous desire to opportunistically waste someone's limited time for their own potential gain. You conflate legitimate albeit casual shoppers with people who are only there in a cynical ploy for self advancement.
The theoretical potential for referrals is a red herring. That same potential exists in the customer they missed talking to, who might actually buy a car, that they lost because someone thought it would be educational to waste their time. Do you know anyone who has sold cars for a living? I do. I grew up with one I call "Dad". I know a lot about how the industry works, dealership marketing and promotions, all of it. So you reference foot traffic as a side benefit to your plan for negotiation experience? Hardly. 5 or 6 of your students in negotiation a day would be enough to cost salesmen money without adding to that "we're busy" look the dealership may want.
Otherwise, selling cars tends to be a soul crushing grind. At times it pays little more than minimum wage for work hours that would rival a dedicated startup team. The national average places their salary between $22,000 and $45,000. That's with commissions counted in and with a work week of 60-70 hours. That's not even counting the off-hours work like delivering a car on a trade between dealerships that is a dead loss for them. Working in the industry means making your target one month only to have the dealership owner change the compensation plan because people were making too much money, and actually tells the staff that's why. At least that owner was honest, most don't bother.
Yeah, some salesmen are wildly successful and make lots of money, some sell high end cars in affluent neighborhoods. But it's like the startup world: for every success like that, even a mediocre success, there are countless others that aren't.
So if you want to brush off this type of behavior as no big deal, at least understand what your really advocating people do. I on the other hand see your advocacy for this kind of behavior as emblematic of the worst impulses of "all about me" culture, and the thin end of the wedge towards condoning sociopathic behavior that looks at other people as merely transactional units there to provide you with something you want.