A few thoughts...
That 80% number may be true when you look at the number of EMS runs vs the number of suppression calls, but that doesn't tell the whole story. There are several different types of incidents that dispatch multiple suppression units, such as a box alarm, an inside gas leak, a Hazmat incident, an alarm bell, or a brush fire. A box will have a supp/EMS ratio of 9/2 in this county. Gas leak, 4/0. Alarm bell, 3/0. Hazmat, 2-5/1. Brush fire, anything from 1-infinity/one or two. A more accurate measure would be to take all the different units, count each call, and then tally the results for a proper fire/EMS ratio.
The more you move from urban to rural, the more relevant fire becomes with providing EMS.
Today, I worked IFT with an EMT that vollies for the Woodstock Rescue Squad in Shenandoah, VA. Originally, he told me that Shenandoah County was mostly a farming community. Then, retirees and professionals with money from DC and Northern VA began to migrate there, drive up property values, and demanded urban level services RIGHT NOW. The county's volunteers couldn't keep up with the EMS demand, so the county had to hire career FF/EMT's and FF/medics. Why dual? Because they can't possibly fund the hiring of seperate fire and EMS, so they have to combine roles.
I work in a fire based system, on a bus that provides frequent mutual aid into Loudon County, Sterling in particular, which is all volunteer fire and EMS from what I've been told. About 25% or more of my call volume is into Sterling's first due. They have BLS, Trauma (EMT-Enhanced), and ALS units. When they get out is hit or miss, but they rarely have ALS on the overnights. Loudon County built and provided 24/7 career staffing in Ashburn. That crew told me that they run into Sterling often themselves. The volunteer system can't keep up, and having seperate career EMS and career fire apparently cost effective for them, or they would be doing that already.
As a contrast, NYC has seperate fire and EMS. Yes, FDNY EMS is technically fire based, but they are seperate from the Jakes. In addition, there are many hospital based EMS providers in the city (my background), maybe 30% of all units, by my guess. If you care to count, here's where you can do that:
http://www.fdnyems.com/EMS Unit Location Charts.pdf
In urban systems, seperate services work better. Units are stacked close together, the hospitals are close, and the tax base can support seperate services.
My point of all this is, every location has it's own unique situation and needs. It's difficult to paint the entire EMS realm with the broad brush of generalization. For every Florida, DC, and CA, there are many places that would be SOL without fire to help out.
Edit: Also, no matter how well modern technology and fire prevention reduces fire's call volume, it will still take the same amount of time to respond to the incident. Keep in mind that modern homes have a fire load that consists of synthetic materials inclusing plastics, that burn much hotter and quicker than legacy homes, which are mostly class A materials, which is wood and cloths. Modern type 5 homes also have huge void spaces. My point? Homes can be charged with smoke filled with dangerous gases such as CO, Hydrogen Sulfide, ans Cyanide much quicker than in the past, and rooms can flash in a matter of a few minutes. In fact, when you compare a legacy room to a modern one, the former takes over 1/2 hour to flash, and the latter takes less than five minutes. Cut staffing and deployment, and help will be too late.