Their coffee tastes awful for the same reason that McD's makes awful food: it's optimized for standardization/consistency.
Starbucks roasts all their coffee to relatively exorbitant degrees to cover up the inconsistency brought about by their very-multi-origin sourcing.
Some Starbucks locations sell "single origin" coffee which tastes quite a bit better, if only because they don't have to hide the variance in taste and can afford not to roast it to hell.
I can grab a coffee and sit down with my laptop in Portland, Boston, or Yuma, and I will have the exact same mediocre experience. I don't care about having a transcendent coffee journey; I care about getting a predictable cup of coffee, a kinda-comfortable space, and wifi to check my email. That's it.
I can hunt for some coffeeshop that might be great or might be awful, or I can head into the local Starbucks and know exactly what I'm going to get.
So, instead of taking the 50/50 chance of something being great, you'll accept downright poor instead.
I'm not actually poking fun of you, one of my friends has the same attitude - something that I just can't understand. I'd rather try and find something that was decent than something that's not.
Sounds like for the OP the coffee isn't the product, but rather a space to work and think.
Having to choose a coffee show, see if they have wifi, charging, not to noisy etc. is an inconvenience if you want to just get started on something quickly. You might only have an hour before a meeting if you are travelling for example.
