This is a sign that someone isn't into you, not into you for the long run, which can happen even in a relationship. And it all boils down to whether or not they want to discuss the future with you. Do they enjoy thinking and talking about a life with you, or do they prefer to live in the present? Because the future can only be one of two possibilities, it could be a promise or a threat.

Someone who isn't really into you sees the future as a threat that will gradually make them unhappy. But when you truly love someone, the future is a promise. It's like a horizon into which you can sail. You're not sure where you're going, but you know you want to travel together.

So, they're interested in you if they want to think and talk about the future. If they avoid or refuse to discuss the future, it's usually a sign that they're not interested in you