As for analogies about cam-viewers. Ok, I can see your point about the restaurant and theater analogies not working because there is physically not enough space for unlimited viewers. I can also see your point about the theater being a 'pay-to-enter' venue. But your analogy of a park doesn't really work either, cause police will kick you out or arrest you for loitering.
Let's try this one on for size: Say there's somewhere that does charge an entrance fee (like an upscale museum gala), but every ticket-buyer gets to bring a "plus-one." Not every ticket buyer will be bringing a Plus-One. Basics and non-tipping members are like the guys who stand on the corner and ask every person entering the museum if they've got an extra ticket. Essentially saying, "Come on, man, you've already paid! You're not even gonna use that extra ticket! Just let me tag along!" Of course, it won't matter to the museum whether you go in or not because they've already made their money, but the ticket-buyer is going to resent you. Why should you get to go in for free when he had to spend $XXX amount to do so? If it became obvious that half of the people who got in were just random people off the street begging for tickets, most of the ticket-buyers would stop going. The museum would either have to lower the price of tickets or stop allowing Plus-Ones so that the purchasers feel like it's an exclusive club again. Definition #2 is the best description for people in these scenarios. If you notice, the term "bum" is also used in other ways, almost all with negative undertones. No one likes covering for someone else's ass when they're so disrespectful that they don't even appreciate it anyway.
Let's try this one on for size: Say there's somewhere that does charge an entrance fee (like an upscale museum gala), but every ticket-buyer gets to bring a "plus-one." Not every ticket buyer will be bringing a Plus-One. Basics and non-tipping members are like the guys who stand on the corner and ask every person entering the museum if they've got an extra ticket. Essentially saying, "Come on, man, you've already paid! You're not even gonna use that extra ticket! Just let me tag along!" Of course, it won't matter to the museum whether you go in or not because they've already made their money, but the ticket-buyer is going to resent you. Why should you get to go in for free when he had to spend $XXX amount to do so? If it became obvious that half of the people who got in were just random people off the street begging for tickets, most of the ticket-buyers would stop going. The museum would either have to lower the price of tickets or stop allowing Plus-Ones so that the purchasers feel like it's an exclusive club again. Definition #2 is the best description for people in these scenarios. If you notice, the term "bum" is also used in other ways, almost all with negative undertones. No one likes covering for someone else's ass when they're so disrespectful that they don't even appreciate it anyway.