But since this doesn't seem to be the case, maybe there is something more to it than what your personal experience is leading you to believe?
I'm fairly convinced it just comes down to laziness. I'll give a real example of something I've done that could be done but simply hasn't been done. I work in engineering, and a lot of this involves printing AutoCAD drawings to PDF files. For a particular project, there are about 10 drawing sets. If I use AutoCAD's built in "publish" command, I can do one set at a time, but I can't queue up multiple sets, and I can't do multiple in parallel. The next step up from there is Bluebeam PDF. This program integrates with AutoCAD, and it does allow me to queue up multiple sets, but it only does them in series. Writing to PDF is completely CPU-limited, so I should be doing 4 of them at once. I can't do that with Bluebeam. Why? Nobody knows. How easy is it to do this? Here's how:
publish_everything.bat:
start "" "C:\autocadpath\accoreconsole.exe +publish "C:\sammy\drawing_set1.dsd"
start "" "C:\autocadpath\accoreconsole.exe +publish "C:\sammy\drawing_set2.dsd"
start "" "C:\autocadpath\accoreconsole.exe +publish "C:\sammy\drawing_set3.dsd"
start "" "C:\autocadpath\accoreconsole.exe +publish "C:\sammy\drawing_set4.dsd"
start "" "C:\autocadpath\accoreconsole.exe +publish "C:\sammy\drawing_set5.dsd"
start "" "C:\autocadpath\accoreconsole.exe +publish "C:\sammy\drawing_set6.dsd"
start "" "C:\autocadpath\accoreconsole.exe +publish "C:\sammy\drawing_set7.dsd"
start "" "C:\autocadpath\accoreconsole.exe +publish "C:\sammy\drawing_set8.dsd"
start "" "C:\autocadpath\accoreconsole.exe +publish "C:\sammy\drawing_set9.dsd"
start "" "C:\autocadpath\accoreconsole.exe +publish "C:\sammy\drawing_set10.dsd"
Double click that batch file. Done. These Bluebeam guys were smart enough to write a PDF program that gets rave reviews, and they still couldn't put in 5 minutes of effort to allow publishing in parallel. The program I wrote to do this just creates a batch file, runs it, waits for all of them to finish, and deletes the batch file. If you're a real coding gangster, you can probably make it run all of those without creating a batch file.
While I'm bitching about Acrobat, I should ask why commenting is so painfully slow. Make 20 comments on a page, select all of the comments, right click and go to property, and check the "locked" box. It will freeze for maybe 5-10 seconds. Why does that take so long? It's acting like the entire PDF needs to be re-written.