What to tell recruiters if they ask why are you still applying while having an offer in hand?

Why do they know you have offer in hand? Why are you telling them?

I am in the same phase, I just tell them one good thing about their company. If its a startup I tell I would like to take up more responsibilities and work in a fast paced environment. If its bigger company i just say I would like to work on scale and stuff like that

Almost always works

Tell them you are looking for better opportunities and be ready with something specific about that company which would sound more believable.

Even though they would most probably see through it they would like the smart tactics you used to add that angle of something about that company.

Why not just tell them the truth and state that you’re looking for even better opportunities.

Double edged sword - there is no right or wrong answer, but they want to see if you will be doing the same with them. Best to avoid letting them know that you have another offer. If not possible, then just say that you did not have the time to fully evaluate the market before getting the first offer and hence you are trying to figure out if that was the best value of your skills

I usually tell them I'm looking for better opportunities.