Why is Batman wearing a speedo?

Short promp... more like a bet

‘Why is Batman wearing a speedo?’ asked Catwoman to Gordon as she saw the superhero standing in the rooftop, almost completely naked, with only the weird piece of clothing and his cloak. ‘We found out that’s Robin’s favourite piece of clothing’ said the inspector very seriously ‘That doesn’t make sense, why is he wearing it?’. ‘Oh’ exclaimed the inspector, ‘it’s just, we started mocking Robin about his ridiculous underwear and he started blushing and arguing about how comfortable so we made a bet’ he said. ‘What’s the bet?’. ‘Robin gets to drive Bruce’s Ferrari for a week if Bruce finds it comfortable’. ‘That’s a silly bet’ she said suddenly turning to find Batman almost naked in front of her ‘Gordon, I  have lost’