I don’t read the sonnets because they are nice love poems. There are a few of those, but a lot could just as well be called anger poems or excuse poems. Some of the best sonnets, like “When my love swears that she is made of truth” and “A woman’s face, with nature’s own hand painted” make cynical fun.
I don’t read them because they are particularly good for imagery. For every “kissing with golden face the meadows green” or “and sable curls all silvered o’er with white” there are three lines like “who do not do the thing they most do show”.
I don’t read them because I think they’re truthful. He says, “My love shall in my verse ever live young”, but who sits around thinking about how attractive Shakespeare’s beloved was?
That is to say, I’ve spent quite a bit of time on the sonnets, but I find it really hard to say why.