One problem is that most RAW converters allow non-destructive editing - the original file is untouched and changes are recorded in a sidecar file and/or a database. That's not too difficult with basic tonal and colour adjustments, but becomes very unwieldy with selective edits, layers, etc.
The original paradigm of LR was to be an all-in-one application, which is why the actual conversion to TIFF/JPEG was hidden away in an Export function that wouldn't run in background. They thought that you could used the (adjusted) RAW for everything and would never need to convert. That was a little optimistic, to say the least, and LR is still a long way off that. Even if they include lens/perspective correction, better noise filtering, etc (as found in some other converters) that still leaves layers, selections, masks, etc which need a conventional editor.
IMO it's a shame that Adobe have monopolised the 'serious' photo editing market - some of the prices are just silly, especially over here - and I'd certainly suggest looking at alternatives because there are some very good ones.
