You could go that way but it introduces an extra step and overall extra complexity in file handling and a big part of the value proposition of something like Lightroom is making the photo editing workflow as painless as possible.
It is hard to describe how valuable that workflow simplicity is but it is a real thing; if I had to RAW process and edit all my photos using DPP (Canon's RAW editor, for my 70D), or Sony's RAW editor (for my A7) or even RawTherapee (an open source RAW processor that actually does a good job of supporting lots of RAW formats), I could do so, but yet I pay Adobe $10 a month to give me a really nice workflow for all of this.
It certainly wouldn't be impossible for a Pixelmator-like competitor to emerge for Lightroom, it'd just be a lot of work for a small team; perhaps more work than it would seem at first blush since there's a lot of complexity hiding behind a relatively simple UI there.
It is hard to describe how valuable that workflow simplicity is but it is a real thing; if I had to RAW process and edit all my photos using DPP (Canon's RAW editor, for my 70D), or Sony's RAW editor (for my A7) or even RawTherapee (an open source RAW processor that actually does a good job of supporting lots of RAW formats), I could do so, but yet I pay Adobe $10 a month to give me a really nice workflow for all of this.
It certainly wouldn't be impossible for a Pixelmator-like competitor to emerge for Lightroom, it'd just be a lot of work for a small team; perhaps more work than it would seem at first blush since there's a lot of complexity hiding behind a relatively simple UI there.