I'm not disputing what you said in your first sentence. In fact, it makes sense. Social Security was designed to be collectively self-funding, but with a uniform payout. Logically, since financial circumstances vary with the individual, that means there had to be some people who paid more than they got in - just as there have to be some people who get more out than they paid in. Anyways, realization of that fact makes it very clear as to why Social Security has been compulsory. If the poker game can't stay solvent without the patsies, and is run by the government, it's inevitable that the patsies will be bound by law to stay in the game. What made it tolerable was the patsy earned more than the non-patsy, so the net beneficiaries benefited from sympathy for the fellow who has less and (to a degree) resentment of the fellow who has more.
But your second sentence is a quantitative statement. According to this link, the unfunded liabilities of Social Security alone (i.e., excl. Medicare) are $8.6 trillion over the next seventy-five years. If it were true that the shortfall was caused by piling on unpaid-for benefits, then the net present value of those unpaid-for benefits over the next seventy-five years would be equal to the $8.6 trillion shortfall. I don't have the exact numbers on me, but this 2010 report does distinguish between SSDI and regular Social Security. It says that SSDI "trust fund" is expected to run dry in 2018, which does add to your case, but it also says that the allocation reserved from regular Social Security will run out in 2041.
In other words, SSDI is only part of the reason behind the unfunded liability. Even if it were eliminated tomorrow, Social Security would still be heading towards the shoals albeit more slowly.
As I said earlier, I believe you when you say you paid more than you'll ever get out. But the way the numbers work, that isn't true of every Social Security recipient excluding SSDIers. It looks to me like good ol' human nature is kicking in, if you get my drift.
As a sidebar, you're experiencing life as part of a government-mandated collective. It's not all that coincidental that there's so much collective guilt floating around, given the number of purveyors of collective 'solutions' and collective 'justice'. Back in the day, rock-ribbed Protestants decried collective-guilt mongering as an excrescence of "Papism."
SOME DIE!
It’s really worse than just some folks getting more than they paid in. For example, under SSDI, if you die young and have minor children, it’s my understanding that those children have benefits at least until they reach majority, and I don’t think that was a benefit at inception. Then there's the matter of illegals claiming SSDI when they haven't paid in much if anything. I would have been willing to take my chances with the equities market over my lifetime had I been able to opt out of SSDI and made my own way to retirement with my own money.
And just today, I read a piece about the next “move” the RATS are going to make is to “expropriate” our 401k’s (and the other “400 series” self-funding retirement gimmicks) that have been set up with the knowledge that SSI will fail at some point. There is reportedly $3 trillion in these accounts that the RATs can’t wait to get their hands on. The plan is to confiscate this money and give the “former owners” an annuity. Then what will happen is that they will immediately piss all this money away and ergo, a second SSI program goes bust! I am 72! I retired at 66. My 401k paid us 15% until 2007. We actually did not spend as much as we were making. SSDI didn’t matter. Then when the crooks on Wall St. stole the citizens assets in 2008, we took a 30% dump in my 401k’s value, and now what’s left is only earning 6%. So our retirement picture has been fundamentally changed at a time when we are not in a position to work our way out of what’s happened. It is therefore, my fervent hope, that the morons who voted for these Marxists start feeling some real financial pain.