Even a house you know you're not going to buy is worth taking a walk-through if you're already there and the agent has prepped it for showing.

You can learn a lot from such experiences. What to look for/what not to look for, etc. Sometimes the wrong location will have the right house and you can dial in precisely the things that matter to you so you waste less time on future showings.

Of course if you're highly experienced and on your 4th house purchase the value for your time may not be there. But I've found it quite useful over the years - especially when looking at different property types than I'm experienced with.