why did huck decide not to run away in the beginning

Huck decided not to run away because Tom told him he was starting a 'band of robber's,' and that if he didn't stay with the widow and become 'respectable,' he wouldn't be allowed to be a part of it.

"The Widow Douglas she took me for her son, and allowed she would sivilize me; but it was rough living in the house all the time, considering how dismal regular and decent the widow was in all her ways; and so when I couldn't stand it no longer I lit out. I got into my old rags and my sugar-hogshead again, and was free and satisfied. But Tom Sawyer he hunted me up and said he was going to start a band of robbers, and I might join if I would go back to the widow and be respectable. So I went back."