That's the point, mate! I remember that I've had to give a security deposit of 120 EUR for renting an apartment for 2 days in Barcelona. I've got them just when I was heading to the airport. Screw this, I want to spend all my hard-earned money during my vacation or weekend!
Jeez! I'm not into big speeches usually but if, say, every tourist in Barcelona would be offered such guarantee for an extra few euros and they would have their ~100 EUR on their hands ready to be spent, I guess it would be good even for Barcelona's economy in general. Not a big deal, but nevertheless.
People have more control over their money, local businesses get an extra buck, businesses like Bailsman operate, their partners get their share, landlords have all their possible problems covered... Win-win!