How come people are not acknowledging me on facebook?

[James]

I dont use facebook a huge amount, mainly just to stay in touch with friends across the globe. I dont have a huge turn-over of friends. I did add somebody about 10 months ago, and send them a personal message too. When I go to their page it still says 'friend request sent' and the personal message still does not say 'seen' next to it. Another person I added two weeks ago is showing the same things in exactly the same circumstances. Now both these people are people who I am sure would be happy to be contacted by me. And they have both accessed their accounts since I added them, as evidenced by recent activity.
I have successfully added a few people, and vice versa over that time frame. I am just a little perplexed that I have seen no action on the other 2 given they were both good friends (unrelated to each other) for the period of time I was with them 2 years ago.
Could it be anything to do with privacy settings, theirs or mine? Any other suggestions would be greatfully appreciated please!

[Jordan]

SAD!

[jesus_disciple777]

They just have better things to do with their time than spend it all on useless apps in Facebook.