I agree that cost notwithstanding, it generally makes more sense to extend the modality that is already there, as opposed to forcing a transfer, at least where some significant riders are continuing on in that direction. (I will not digress to Scarboro or Sheppard, although I am certainly making an effort to allude to these). In this case, I'm not sure what transfer you are objecting to - Eglinton West to ST to downtown? or Eglinton West to Crosstown to midtown? Can you please clarify?
If you are saying there aren't many people coming east along Eglinton from Etobicoke, I would agree at present, but I do expect that will change with Crosstown, especially if it did go west to Kipling or Martin Grove (at least). There are a lot of people from the residential areas along Eglinton West who work downtown today, but who would be attracted to jobs around Eglinton and Yonge if the transportation were better. It's a situation where build- it- and-they- will- come applies.