There's a difference between forcing and encouraging, though. And I feel it's important that all children know they are basically ok in their parents' books. With my own quiet and reluctant to chat DCs, I have never used the term 'shy' because I think it's not a good idea to label children, even with something complimentary. First person to use the word 'shy' for any of my DCs was exMIL who tends to make personal remarks about people (rather rude, imo) an unhappy day for oldest DD (who had blushed in response to a remark about her red hair), who was thus singled out in quite a large group, by her grandmother, using her usual loud voice, and who had everyone's attention, as being 'shy'. The perfect storm, you might say.
DD and I talked about the incident and I assured her she was ok in my books, she had a right to her feelings, everyone feels the same way when grandma puts them on the spot like that, not just her. I have taken the approach of reassuring my DCs that they can smile and make eye contact, no need for clever repartee if they don't feel they can do it, need to say please and thank you though, and there's nothing wrong with them for feeling uncomfortable talking with adults.
I have three shy DCs and two who are more outgoing, only one of whom has what most adults would consider a charming manner, though the younger of this pair is getting there. The oldest two (who are among the shy ones) are fine now, though quiet, through acceptance and encouragement and exposure to situations where they didn't have me or my skirts to hide behind, especially through school and in sports; the other shy one is really, really shy, moreso than the oldest two, but is gradually coming out of her shell -- if she was my oldest I would have possibly sought professional help with her, but I'm confident having seen the others come along that she will be ok, and will feel ok about herself, which is what I'm aiming for really. The other two, who are social butterflies, went through patches when they lived in their own little world or had insecurities to deal with too; nothing is ever really in a straight line with children.
I was treated probably the opposite of LeQueen's SIL by my well-meaning parents and hated the feeling there was something 'wrong' with me because my instincts were constantly being overridden and overruled. Elocution lessons were a nightmare, ditto elocution exams (went to that sort of school....), but I think a bit of empathy might have gone a long way. Yes, I got over it, but I wouldn't go the same route with my DCs. I would put them front and centre and not the expectations of others.