My Brother (or Sister) in Christ: You are taking advantage of a system to save money at the expense of other passengers who spent that money for the same privilege. The airline will not tell you no. That doesn't mean you won't be judged by the rest of us for it. If you don't like that, don't brag about how you work the system.
As for the families-with-kids-who-don't-buy-seats: I don't really see this, and I fly a lot. Delta deals with this in part by blocking the last couple rows of the plane until they start clearing Basic Economy seating; presumably they use those seats for these situations. It's still not a guarantee, and so most families appear to be willing to pay for seat assignments so that they don't have to worry about it.
There are a couple of other spots they block before clearing too--often the rows right by the lavs, and occasionally a pair of seats in a bulkhead.