The current residential code in Florida is the 2007 Florida Building Code - Residential (
Section R606 (page 6.47) of this code governs masonry wall construction. For the purposes of design and construction, this section takes you to the referenced standard (ACI 530) and/or to the provisions of the 2007 FBC-R. Lower construction costs will typically result from prescriptive provisions. So, being the businessmen they are, contractors will do their best to provide structures that utilize the prescriptive provisions.
Section R606.7 of the 2007 FBC-R only requires horizontal joint reinforcement for "stack bond construction", not "running bond". One-story structures utilizing running bond construction that is, for the most part, ungrouted and unreinforced is typical.
The above statements should answer all three of your questions.
However, just because the code allows it, just because it is standard practice, just because we are not seeing widespread collapses of residential structures, does not mean it is a good idea.
Given the combination of loose, sandy surficial soils, the widespread lack of gutters on roof eaves and/or code-required downspouts discharging water away from the foundation, the widespread lack of code-compliant site grading, the widespread lack of control joints and ungrouted/unreinforced masonry construction, stairstep cracking distress (due to slight differential settlement of the supporting soils) is very common in the walls of residential structures. When a homeowner that lives in Florida observes this type of distress, and particularly after they have seen billboards sponsored by sinkhole attorneys (and/or they have learned about sinkholes from their neighbors), they file a claim with their homeowner's insurance company.
Many times, the insurance company-sponsored subsidence investigation "cannot rule out sinkhole activity" (very loosely defined), and expensive remediation of the subsurface is required (many times exceeding the replacement value of the structure). This drives up insurance premiums for everyone in the state.
Shoddy construction practices, in part driven by weak building codes, lack of thorough plan check procedures and building inspections (by the jurisdiction) don't just cost the individual homeowners, but also everyone else who pays for homeowner's insurance in the state.