1) FCC wants to be able to monitor our transmissions.
2) Data modes are not permitted in the HF voice subbands. It is not good amateur practice to put wide modes in the CW/data subbands. There are also restrictions on data rate and frequency shift. End result is a the data modes US ham use tend to be narrowband.
On Point #1 I agree with the FCC, there should be nothing that we transmit that we should feel secretive about. The FCC regs are a pretty good guideline on prohibited information (business traffic, broadcasting, certain types of personal information during a disaster response/ relief operation).
On Point #2 there is a bit of a loophole on ALE transmissions. It has been debated that ALE is classified as a voice mode. To quote the FCC "Incidental tones for the purpose of selective calling or alerting or to control the level of a demodulated signal may also be considered phone." You can find a reference to this distinction at; http://hflink.com/articles/
According to the FCC we are limited to 300 baud for "digital modes" in the HF spectrum. This data rate may have been relevant when working with FSK keying where the Shannon limit was very low. With advanced modulation techniques (modulo-N, the varieties of PSK and STANAG-like systems) we should draft a recommendation to the FCC for rule-making to make the standard indicate "any data mode that can be constrained in a 3 KHz SSB channel that does not use techniques to mask or encrypt the contents"
Again, that is a personal opinion on digital modes and I will shift further discussions of that over to the appropriate forums.
Tisha Hayes, AA4HA