Alright, it hasn't happened for you, yet. But, even with a +3 hard, there's an 8 percent chance of a 6-. For those with a +1, that jumps up to almost 28% chance of a 6-. We aren't talking about something that isn't supposed to be part of the game. Heck, the entire engine is built around 10+, 7-9, 6-.
A possible scenario. Keeler the Gunlugger is given the job of driving the Hombres Gang away from the only well in 50 miles. (Keeler has 0 advancements, he's a new character. But, she has picked NTBFW, Insano like Drano, Bloodcrazed and has a MG and heavy (2) armor. She doesn't just look tough, she is tough). Keeler has already killed the leader of the Hombres and several of his bodyguards, but not before they got a call out for the rest of the gang to come back and kill this crazy woman.
25 tough bikers roll up to the well (small gang, 2-harm, 2-armor, because they recently found a cache of kevlar body armor). Keeler is just finishing patching up a cut on her arm and doesn't hear the gang until they are almost on her. The gang sees its dead leader and open fire at the same time as Keeler unslings her still-warm MG and strafes the area. Keeler rolls Seize By Force, because she wants to maintain control of the well and the Hombres are only getting paid if they hold onto that water. Keeler rolls snake eyes and even with her +3 Hard, still just gets a 5. Bad luck for Keeler. Or is it?
Keeler doesn't want to lose this well. This is her first job and reputation matters. She chooses to maintain definite hold of the well. Keeler does 4 harm to the bikers minus 2 because they are exceptionally armored. They do 2 harm to her, but she also has 2 armor. Keeler's roll of a 5 ends with many injuries, some serious and a couple of fatalities for the Hombres. They have no leader, so they break and try to get out of there as quickly as possible. Possibly to plot revenge, but if this is how well they managed on Keeler's unlikely roll of a 6-, things aren't looking good for them. Keeler takes 0 harm and has to roll the harm move. Granted, this can still go poorly for Keeler, but it's relatively unlikely. (When she gets her first advancement, she can take the juggernaut move to mitigate this).
On a roll of 6-, Keeler wins. She kills some, hurts more, drives off the gang. She's likely unhurt. Shouldn't the failure on the SBF mean more than this, even for a tank-like Gunlugger?