Well, here's a little counter-argument. Up until this point, the Empire had no conclusive idea that the Falcon's hyperdrive was busted. I'm sure they might have figured it out, but there was nothing to prove it. Yet they'd still spent the first half of the movie causing destruction for the Empire's fleet. They caused several TIEs to be lost in the asteroid field. They'd caused a few Star Destroyers to sustain significant damage in said asteroid field. And they almost caused three Star Destroyers to crash into each other! For all they knew, the Falcon's crew could be suicidally insane or at least have some kind of plan as to why they were screwing around with the Empire instead of escaping. So maybe they were just being cautious, and that's why they decided to force Lando to trap them instead of continuing to attempt (and failing miserably) at trying to capture them themselves. It makes perfect sense to me.