What's the point of bidding on Marktplaats?

I often place what I think are reasonable bids on second hand items listed on Marktplaats, but sellers never respond to these. I see that many listings without a 'buy now' price go for months with many bids (weeks apart) on them without the seller finally accepting one and carrying through with a sale.

If there's no closing date and the sellers don't respond to an offer, what is the point of bidding on anything on Marktplaats? And what are these sellers thinking?