i think it's one of those things where just because it's done before and because everyone else does it, then it must be right.
it's ludicrous that in this age of permanent internet connections - and even being able to get webpages on a phone! datasheets should be 'live' on a website, (printer friendly of course) ... as they can be updated in realtime for all instantly.
Obviously, it allows full control over the page layout, images and fonts, and for some content, that's very useful. In addition, some documents are created in a word processor or graphics package, which has package-specific file types, and these are not necessarily share-friendly, whearas a PDF is likely to be more compatible. HTML just doesn't give you that 'control' or that 'flexibility.'
But, who then is responsible for producing, updating and maintaining the pdfs. It seems to me that it would have to be engineering, rather than the web department!
The datasheet is something that you might want in your hand when working (depending on the product) so a print format is probably a good idea. A common database structure for technical info on a disparate product set is a separate issue and again not a web one. There are ways around this but it takes you into some fairly obscure areas of data modelling. If you have some skilled entity relationship modellers in the company then drop the problem on them.