No rude, No worry that offering is always very good.
Basically most(99.999%) elders feel/think yr offering is "welcome","thanks" usual.
But in packed train will be very difficult getting off if seated.
Just by such a small(?) reason mostly.
(depends on seat position near door or not and passenger amounts)
And also just cannot explain/say true reason well/shrot in EN especially fr foreigner's cases.
(You said in Japanese?)
Also some other reasons exist.
- Just thinking "I'm still young" but no angry a bit not glad "looks so old?".
- Body no good somewhere for sitting/standing mainly waist,hip,knees/leg/foots damaged/pain with usual.
(Somtimes feel "a baby is heavy" in mother case similar reason)
- Came from out of urban city or last taking tain long years ago need to confirm train operating section/position
so would like to keep watching "railway map" or operating info "monitor".
- Just thinking need to escape "comfortable/lazy" from insufficient exercise life.
- By "diabetes?/糖尿病(tounyou-byou)" or something serious sick reason need enough exercise keep walking mainly.
(Have you ever seen such walking arond man/woman at no packed train passage?)
- Just waiting good scenery or something check item/point coming
would like to see from car window as one of small "my rule"/custom/habit.
- Only in underground train no good scenery would like to read ad.
(train small poster type ad calling "中吊り広告/nakazuri-koukoku")
"ad" provides a lot of newest info for daily life news of service and products mainlyhttp://www.zassi.net/nakalist.cgi
Also reading "Kanji" good for "Anti-aging" and "vision/eye test" easily.
(Photo also make to think "Who?" for "my memory" out quickly my answer is correct or not)
Baby mom case if baby not sleeping need to watch carefully and must move quickly
if something accident(?) happened. (crying,milk,pee or)
Anyway no need thinking so serious :)