When a politician/celebrity resigns or steps down do you consider it an admittance of wrong-doing?

That's a hard one to answer... In most cases, I would say yes. But I'm sure there are some cases where one was falsely accused of something and they stepped down because even though they know they're innocent, they know the seriousness of the allegations would destroy their reputation so they feel they may as well resign.

I think it usually means that if more is investigated it would be worse. It's kind of like saying enough is enough.

I think sometimes if they’re under contract, leaving won’t be their choice. I like to go with innocent until proven guilty. But it does instill suspicion for sure.

The thing I don't get is all these accuzations, no real proof, so yeah it is kind of admitting guilt

Depends on the audience. If you are a liability then admit and resign. If your seen as a hero deny.