Mutual gift-giving is an ancient human custom that builds bonds between people. I really like giving and receiving gifts, but I can't help but feel that it's become a lot more complicated these days when a gift of a pretty shell just doesn't go down so well as it did 20-odd thousand years ago.
As we can see on this thread, lots of people have different expectations about gift-giving at weddings. That's where all the potential for embarrassment or disappointment lies.
Part of gift-giving is (or at least it was 20,000 years ago) establishing how important other people are to you, so that they can know that they can rely on you if they need help. Obviously if you are friends with someone you hope that this friendship is mutual, and that you are important to them and can rely on them in return.
When their gifts to you on your wedding day do not meet your cultural expectations it is natural for you to worry that this implies that you are not as important to them as you thought, and consequently to feel disappointed.
Feel reassured that this may be simply because they have become a bit cynical about the giving of gifts in our very commercialised modern world, rather than it being a personal statement about the value they place on your friendship.
When I was preparing for my own wedding recently I became quite anxious about whether we should have a gift list, whether it would be more rude to give guidance on appropriate gifts, or to give no guidance and leave people having to guess. This was complicated by the fact that the wedding gift culture is quite different among my wife's Irish[-American] family and friends than among my English family and friends.
So I wouldn't say that you are being unreasonable to feel disappointment, but I do think you would be unreasonable if you allowed this to affect how you feel and behave around these friends.