God gave the Promised Land to the descendants of Abraham, not because they deserved it, but to use them to punish other nations who were wicked. After he gave them the territory, their job was to drive out the other people (thereby punishing them). Though the nation of Israel did this to some extent, their efforts were incomplete. This was to their detriment and God’s dismay.
God also gave them laws to obey. They didn’t do a good job at following through with those either. Had they completely done all God instructed them to do, he would have given them even more territory: this time because they earned it. Sadly they didn’t do their part, so they never received all the land God wanted to give them. The Promised Land could have been bigger, but because of disobedience, the nation missed the full blessing of what God had in mind for them.
I think it’s that way with us sometimes. God wants to give us more, but we don’t do our part to receive it and so we miss out.