Silly runner bean question

Apropos nothing at all, apart from pure curiosity, I'd love to know why only about half of my runner beans actually grow straight.

I like to chop and change with the varieties I grow (this year I'm trying Red Rum and White Emergo), but whilst I get a good crop, at least half of them are always 'curly'. In some of my, 'mmm, how shall I waste 10 minutes?' moments, I've actually gone round (some) of the plants, identified embryonic beans and made sure they aren't 'hooked up' against stems or anything which would cause them to curl round, but it seems to make no difference.

Over the years I've been to innumerable flower shows and seen the runner bean exhibits, all identical in size and shape and all ... perfectly, ramrod straight - could this be why they have a runner bean class or, as I suspect, do people secretly put them in splints?

 

Yes you are right the show people do striaghten them

 

Splint + wrap in damp tea towel.