Every home built in the last few decades has treated lumber in it to some degree. CCA was phased out because it was determined to be toxic if ingested (by eating the wood or breathing the dust from sawing it) in large quantities. Personally I think it is a joke that they banned it, and the ban was driven by some very fuzzy statistics. It would be strange to build a home entirely of treated lumber, and if that is the case I'd be really really really surprised. I strongly doubt that's the case. Normally the treated lumber will be used in contact with the foundation and the remainder of the home will be framed with untreated material.
From a health and safety standpoint the CCA poses no hazard unless you plan to chew on your walls.
C2 waterborne treated lumber is nearly always southern yellow pine. It is strong stuff compared to other framing lumber species.
Decrease the value? Not sure why....
In 1998 there were no other real options than CCA for concrete contact material in residential construction. Today there's no other option than ACQ or borate treatment for concrete contact. I assure you every house built has it.
The paint on the walls and the dust in the carpet is much, much more harmful to you than the CCA contained within the walls in my professional opinion.