History of bulk electronic components suppliers

Hi,
purely out of curiosity, is there anyone who can tell me what happened to popular electronics mail-order companies of the 1970s like Poly Paks in the US and BiPak & BiPrePak in the UK? There must have been a trend that killed them off, and caused other medium sized names to shrink while a few grew very large? Is there a book on this element of history??

Mark A
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