The record companies don't control the artists or their behaviors. As for why they "allow" the material - I would guess because they think it will be profitable for them.

As for the progression of suggestive material over the years - society in general has grown progressively more apathetic and toward censorship. It's not just that the media has become more racy; overall we're a lot more tolerant. I don't think that's a bad thing. If someone wants to make a racy and suggestive song, let them. They'll face whatever societal consequences needed depending on the content.

Why are you so interested in banning suggestive content?