You're missing a huge issue here - management.

If you provide realistic estimates, it is very likely that management simply won't accept them.

I told a manager once, "If these were real estimates, then on average, half they time they'd be too high."

He told me, "If half your estimates were too high, you'd be fired." Of course, this was the notorious Vinnie Falco, but even less malign managers seem to be more interested in providing friendly, very optimistic estimates than realistic estimates.

In that case, I simply told him what he wanted to hear, and then delivered the software when it happened to be done, and I have done that since with other managers who did not want to hear the truth.

I feel that realistic estimates are only good for a team, but I am no longer going to butt heads with someone who seems them as decoration.

The funny part is that my velocity is usually the highest on the team, so it's not that I'm going to slow the team down.