Stephen Hawking pointed out that if time travel were possible, time tourists would arrive in our time from the future.

It may be possible, of course, that time travel exists in the future but is undeveloped or unused.

There is a senario where you can travel forward and not backaward that could be uesed to explain that or great pains are taken to hide them from discovery.

Would they come to now? It wouldn`t really be very interesting for them, or perhaps they are here but we can`t
see them. If someone could prove beyond reasonable doubt
that they had come from the future would we regard them with
friendliness or hostility? After all, they would know what
is going to happen to all of us, and it might be we`d rather
not know it!