It's similar to a bank foreclosing on a house. The borrower pledges something as collateral for a loan, and if things go south, the lender can liquidate the collateral to recover some or all of the debt. It's not correct to say it's done without the borrower's consent because the original lending agreement allows it when the circumstances arise.

Tangentially related: Martingale betting system (https://en.wikipedia.org/wiki/Martingale_(betting_system)). Aside from its theoretical impossibility, this system typically fails in practice when the gambler hits a house limit and can no longer continue placing bets.

Yes, see sibling comment.