My friend who is almost 29 (next year) she still suck her thumb most of the time when sitting watching television.
Why is that?

It is a habit she never broke, and actually better then biting her nails. I know it looks gross and she is probably not aware of it. If you tell her it doesn't look good and bring it to her attention she just might realize and stop doing it. Get her some suckers to replace the thumb, that might work.

Its just bizarre really!
Is that because her mum maybe stopped her dummy early?

I don't know, we all have habits - mine is playing with my hair - twirling it and that's bad also!
But thumb sucking at 29 yrs of age!

She laughs when I pass remarks..

Why do you think she does?

Subconscious habit, who knows; could be from way back but if she only does it while be engrossed in a TV programme there is no harm done but if she does it while driving, while on the bus, while shopping, then it would be truly bizarre. On second thought, nowadays one can't really afford the germs we get off our unwashed hands. Tell her to think about these super bugs going around now that play havoc with our immune systems. When she thinks of being seriously ill, she may stop doing it.

I had a friend who used to thumb suck a lot,but she would go into her room after school and thumb suck as long as she wants then comes out.
This was when she was in middle school, and her parents tried henna(which she hated) on her thumb,but she did not stop, she just moved onto her next finger.
Seems she just needed to thumb suck.Sometimes she said that she used to hardly be able to wait until she got home to do it.

I think she outgrew it after high school,but since she left school I haven't seen her in a while,maybe she still does it, I am not too sure.

I did ask her though why she did it, her answer was that it made her feel good.

As Tickle said, it must be a habit that happens when your friend is engrossed in something.

I wouldn't worry co I'm 18 and suck my thumb and my partner 24 sucks his thumb to