It's not that BIAB people aren't as open minded, it's just BIAB is BIAB....it is a SPECIFIC technique....it is by nature limited in options - there just isn't much flexibility there. There aren't 20 different sparge methods and mash procedures, etc. However, what it lacks in flexibility, it more than makes up for in convenience and simplicity.
BIAB is a Honda Civic DX with roll up windows and cloth interior. If your point is to make it from point A to point B as economically as possible, i.e. make good beer as economically as possible, it's probably the one for you. Traditional AG brewing is more like an Accord LX with heated seats, power windows, leather interior, power seats, and a navigation system. You have more flexibility, and you like to have more control over your overall experience and more options, and if it costs a bit more $$$ and a bit more time to have more than just reliable transportation, it is worth it to you.
Traditional AG brewing is extremely flexible with hundreds of options developed over several thousand years of brewing. It is by nature extremely flexible with lots of differing techiques and procedures all falling under a generic title.
BIAB is one unified technique, just like batch sparging is one technique and fly sparging is another. That makes it a little unfair to call BIAB close minded, it just isn't developed beyond a few basic options, so it is by nature limited and unflexible. I can still make commercial quality beer in an hour less time than the traditional AG brewers in my club, and haul about 1/3 of the equipment to group brews. They can still pull off a begian quad or barleywine that I would never even attempt with a full volume BIAB.
In my brewclub of about 100 members, we have about 30% BIAB brewers (including me), about 30% extract brewers, and about 40% traditional three-vessel AG brewers.
The BIAB brewers are definitely trending upwards, but just at a creep, not rapidly. When a non-brewer or newbie brewer comes to our group brew days, we make a point to explain everyone's unique systems and techniques. When the extract brewers move to AG, about 1/2 of them are choosing BIAB, and about 1/2 of them are going to traditional three-vessel AG.
I would venture to say the "laid back" brewers typically head to BIAB, while the "detailed" (<--anal..lol) brewers head to traditional three-vessel AG.
All that said, I honestly think BIAB offers the oppertunity for the more casual brewer to move to AG and stick with brewing long term. If the actual numbers were available, I bet they would show that the trends of traditional AG brewers hasn't really changed much, i.e., people aren't choosing BIAB OVER traditional AG, but MORE people are getting into AG brewing overall thanks to BIAB.
In my mind, it is a WIN/WIN for the homebrewing community!