I would say the answer is 'yes'... but not really.
You see, classrooms don't care about high quality first and foremost, they care about getting something servicable in for the absolute cheapest price.
Poor color? Doesn't matter.
Rainbows? Doesn't matter!
Limited connectivity? Doesn't matter!!!
Up to a point, what I am saying is true.
Doing commercial work currently and I can promise you that the government has zero interest in HDMI or DVI connectivity. They want VGA (5 BNC or 15-pin connection) and composite. Two, and only two types of connectors are all that is required.
You say "Well, what about consumer devices like Blu-ray coming out that may require it?"
No, there is no format that REQUIRES HDMI currently, or even proposed. There are those that require HDMI for the highest quality output possible. That doesn't mean that you can't use the same composite video connection you have used for 20+ years and get the same passable results you have had for 20+ years.
That's the key - there is no benefit to a school, or most businesses, to take advantage of these higher quality connections. The added cost that goes along with it simply is not worth it or beneficial to most companies. Schools especially.
It should be noted that HDMI and DVI have limited line lengths unless you pay even more for optical fiber connectivity. While, RGBHV can be run hundreds of feet over traditional coax or further over new CAT-5 solutions.
I fully believe that the high-end consumer market is driving the commercial market, not the other way around. HDMI will eventually show up on more and more commercial products and DVI is on a LOT of commercial projectors - but not the cheapest ones, because that adds cost. And you are looking at the cheapest ones because they are the most cost efficient.
Price - Price - Price - Price - Price
It does not go hand in hand with quality.
Here is a list of 16 projectors for business - all with DVI (HDCP) connectivity.
NOTE: For home theater, people should have been getting HDCP compliant devices for the last 3+ years as the potential requirement has been known of for that long - or more.