When I was 40 I too assumed it would not be there. At now 62 I’m mostly sure most of it will be there for most of my out-years. But I have planned for not having it, been fortunate and disciplined enough to now be able to do without it, but also mostly expect to enjoy my share of the windfall when it occurs.
As an aside…
The percentages @Tamerlane quotes are enshrined not in law, but in SSA internal regulations / procedures. When those numbers were computed many years ago, the idea was to make it actuarially equivalent whether any given recipient took theirs at 62 or at 70. Across the bulk of the citizens, whether everyone took 62 or everyone took 70 or any mix in the middle would work out to a wash for SSA and their budget. At least that was the theory.
In the intervening years as inflation and risk-free interest rates have collapsed and longevity has increased, these now-obsolete percentages amount to a one-way winning bet for the vast majority of healthy citizens; if you can afford to wait past 62, it’s an awesome almost-guaranteed investment paying a real nice rate. Even if SSA or Congress was to change the rates and rules, there’d be some warning such a change was coming so anyone over 62 at the time could lock in the existing good deal or something close to it.