Why do the Tucks live in such a hard place to reach?

The Tucks live in an isolated area so that people will not notice that they don't age.

Being immortal brings with it a host of interesting problems.  One problem is that people will notice that you never get any older.  Your friends will age, but you will not.  As a result, the Tucks decide to not make friends.  The consequences are just too great.  The closer you get to people, the more questions they ask.

"They come to pull back from us. There was talk about witchcraft. Black magic. Well, you can't hardly blame them, but finally we had to leave the farm. We didn't know where to go. …” (Ch. 7)

As a result, the Tucks live a pretty lonely existence.  Ma and Pa Tuck have each other, of course.  They have their children, Jesse and Miles.  However, neither of the boys can have a family.  Miles’s family left him when they found out, and his wife and children aged without him.  Jesse never risked getting married because he knew what would happen.

Jesse and Miles travel the world, never staying in any place long but exploring and seeing new things.  Their parents live a quieter and simpler life at home in their cabin.  Since they have lived there so long it is a little chaotic, but homey.

Mae and Angus are comfortable in their house, but they know they will not be able stay there forever.  They have to keep moving in order to avoid suspicion.  Mae explains to Winnie that Angus is very attached to their house.

Then, too, it's off by itself, plenty of fish in the pond, not too far from the towns around. When we need things, we go sometimes to one, sometimes the next, so people don't come to notice us much. And we sell where we can. But I guess we'll be moving on, one of these days. It's just about time." (Ch. 10)

Sadly, the Tucks do not get a chance to make a quiet move.  The man in the yellow hat finds them, and in the altercation Mae accidentally kills him.  She is going to be tried and possibly hanged, something that they really can’t let happen.  If May were to be hanged, she wouldn’t die, and the secret would be out.

The Tuck's house is symbolic of their existence.  It is removed from other people, but it is full of nature.  It is comfortable and focused on what matters to them.  The Tucks get by, and live a harmonious life, but they live it by themselves.