Um, you have the same number of options as you did in the last games. You only had two in Origins (Leliana and Morrigan) and two in DA2 (Isabela and Merrill.) For the first time in BioWare history, gay and lesbian players have two options as well for the romances. Straight women got 4...if they play an elf. They have 3 if they play a human and 2 if they preferred qunari or dwarf.
Every Inquisitor isn't bisexual, that's a little absurd. If that was the case, why would you be stating your options are limited? If every PC is bisexual, then why are minding having two female options? By that logic, you should have no problem romancing Bull or Dorian. However, from the way you are talking, you sound like you play straight male characters. Which is fine, but the only limitation here on on yourself.
The NPCs may not use those labels, but clearly do express preferences in gender. Cullen will talk about the female HoF if she was a mage. Blackwall and Josie get together <if not romanced.> Bull and Dorian will also become a couple if not romanced. Cassandra talks about her former male lover as well. Think about your causal speech: You don't go shouting to the world you're straight, but you'll mention either previous relationships or attraction to women while taking with friends. It isn't any different here.
Why different archetypes? Well, creativity for starters. Folks like to see the dashing rogue, or the lady warrior with a heart of gold. That is the one of the basis of any storytelling, regardless of medium. Also, please leave the word "catering" at the door. BioWare has stated that they aren't catering to anyone, merely trying to give a variety of options for many people. If you don't see the point, then why did you come by? Archetypes for characters are good things, as they can give a foundation for a character later.
As many of us have stated for months off and on, BioWare is going to have gay, bisexual and lesbian characters in their games. David Gaider moving onto another BioWare project isn't going to change that. Since we have a chance for the devs to read our ideas (and the devs/writers do lurk on the forums,) this is a great time to toss out some thoughts.
There is plenty of threads off and on in the Feedback section that have other requests. This one has been around the longest at this point, because we try to maintain civility and stay on topic.