"He'll be safer in the Tower, 'Tash. HYDRA won't be able to get to him there." Truthfully, Steve didn't like Bucky being close to loose in the city, with only Natasha keeping him from roaming and possibly getting picked up by HYDRA again. He wanted to help Bucky as best he could but he still wasn't convinced that just keeping Bucky in the city was the best way to do it. He needed somewhere he wouldn't be able to get out of.