Why husband walks 15 meters ahead of wife?

Why husband walks 15 meters ahead of wife?

I couldn't refuse to notice the walking pattern of senior immigrants, especially Indian/Sri Lanka natives.

It was a very warm and sunny day.  I was driving by a prominanet park in New Jersey.  I saw a couple, around 60-65 years old.  The husband was walking exactly 15 plus meters ahead of wife.   I was able to sense wife having hard time walking, she was taking slower steps.  She was not in physical shape to walk as fast as her husband.  

I also noticed that the husband has his head up when he is walking, as if he is pride of his achievements in life.  I've been noticing many couples like this around the neighbourhood.

I'm sure culture has some affect to it.  Is it culture, or is it psychological behaviours?  Is husband shy of walking beside wife? Does husband feel that he is leading the family and want to express it in some form when they are in outdoor scenes?  Is husband feeling that he is giving protection to his wife by walking ahead?  Does wife feel safer, comfortable, and relazed walking 15 meters behind her husband?  Is husband not patience enough to stay back and walk slowly with his wife?

What ever it is, I think the family is very happy together and have lived a very happy life.  I parked my car and watched how long they going to walk like this for.  I noticed they came to a traffic stop and it was green light.  Husband stayed behind and waited for his wife to catch up to him.  As the wife catches up to him at the signal, the light turns red.  Once the light hits green light, husband walks in same speed with his wife to the other side of the road.  After walking few meters with his wife, husband starts to gain momentum and again pauses and keeps a 15 meters distance between his wife.

First I though leaving the wife behind 15 meters is annoying.  Then I realized the husband has his full concentration all around the surroundings.  He is guiding and protecting her.  Wife walks slowly and calmly knowing that guardian is protecting her steps.