Actually it doesn't. The "cross-coverage" costs mostly cancel each other out by having more people pay into all of them. If anything, they add 1 to 3% to premium over limited coverages, and reduce policy preparation costs.
What drives up costs is forcing carriers to insure known AIDs and cancer patients applying for insurance AFTER they have become sick, and who need $100,000+ per year treatments, and then throw them into the same "standard risk pool" with young and healthy family clients.
Actually, if you are in a group plan, the cross coverage can cancel out the costs as you say. For a policy for just one individual, if the insurance companies are allowed to offer options of coverage, it does work against you as I said. That what priced so many out.