I understand where you are coming from too. Ds is now 8 and is definitely affectionate but not in a huggy way.
He likes to sit next to me and I usually get a lovely sensory seeking foot jabbing me or climbing up my arm etc - lol. He will come for a cuddle if he is upset, but only if I suggest or initiate it and it doesn't come naturally to him. It can be a bit like hugging a rather bony statue, but he still gets comfort from it.
He never ran out of nursery/school and hugged me either and it did bother me when he was younger, but then he was the only little boy that walked with his Mum and held her hand all the way to and from school and the other Mums were all jealous of that. I didn't get the running up and hugging with ds2 either for a long time when he was in nursery and I thought I must be a terrible Mum or something (didn't know ds1 was AS at that point.) Eventually we found out that ds2 had really bad eyesight and was unable to spot where I was standing. Now he wears glasses he more than makes up for it and nearly knocks me off my feet running up for a hug after school.
Ds1 absolutely adores his 18 month old sister, she is literally the light of his life - but he doesn't hug her either. He will hold her hand, sit next to her, roll around on the floor with her, sing to her, pat her head, stroke her hair and smother her with kisses, but I have never seem him hug her and he doesn't like her to sit on his knee either. She seems to have learned/accepted this and always gets up to sit next to him rather than climbing on his lap, whereas she is always more than happy to sit on ds2's lap and regularly runs up to give him big hugs.
He also does the affectionate patting, if I am upset he will come up and pat me on the shoulder or head. It makes me laugh sometimes as it just seems so - well - Victorian/British iyswim!
I think for me, it has become easier as he's got older. At the age he is now (just going into year 4) its not considered cool to show affection to your parents, so none of the other Mum's get hugs after school either and I don't feel so different.