When Hermione tried to find an escape, Ron, and Harry side-along disapparated with her to the forest, why didn't Harry call for Kreacher, given the circumstances that the house-elf was now friendlier than ever?
“As we Disapparated, Yaxley caught hold of me and I couldn’t get rid of him, he was too strong, and he was still holding on when we arrived at Grimmauld Place, and then — well, I think he must have seen the door, and thought we were stopping there, so he slackened his grip and I managed to shake him off and I brought us here instead!” “But then, where’s he? Hang on. . . . You don’t mean he’s at Grimmauld Place? He can’t get in there?” THE THIEF 271 Her eyes sparkled with unshed tears as she nodded. “Harry, I think he can. I — I forced him to let go with a Revulsion Jinx, but I’d already taken him inside the Fidelius Charm’s protection. Since Dumbledore died, we’re Secret-Keepers, so I’ve given him the secret, haven’t I?” There was no pretending; Harry was sure she was right. It was a serious blow. If Yaxley could now get inside the house, there was no way that they could return. Even now, he could be bringing other Death Eaters in there by Apparition. Gloomy and oppressive though the house was, it had been their one safe refuge: even, now that Kreacher was so much happier and friendlier, a kind of home. With a twinge of regret that had nothing to do with food, Harry imagined the house-elf busying himself over the steak-and-kidney pie that Harry, Ron, and Hermione would never eat."
Harry Potter and the Deathly Hollows - Chapter XIV (The Thief)
The situations are getting worse than ever. They are being watched as Mr. Weasley said. Yaxley will wonder what's occuring in Grimmauld Place, he could simply check inside the house. Having said that, Death Eaters could torture the house-elf. They can get a big help from Kreacher especially that the elf can get along with them that time.