As pilots, we just don't have enough information, both in terms of exactly what the extent and type of the contamination is and what effect(s) it will have on the airframe. So we de-ice, then maybe anti-ice as well to get back to a known state where we can apply holdover times, etc.
If you're still not convinced, talk to an aerodynamicist or a performance engineer and see their hair stand on end...
What do you not understand???
I've stated I support the SOP for its improvement in the overall safety statistics.
I've stated I do not and have not taken chances with contaminated flight surfaces.
I understand that you were raised with the comfortable blanket of having the decision made for you with the SOP and that making the decision I've made example of is beyond the cover of your blanket with which you feel so safe. I have observed the transition to this attitude you have across the younger ranks which has been artificially created by the SOP. Just as automation dilutes pilot skill, the SOP here has diluted your ability to see and think outside the little box you feel comfortable in. It doesn't much matter in that the SOP rules, right? It only matters when the inability to see outside the little SOP box has you crucifying a colleague with a label of "unsafe" - when in fact he may have been safer and just more experienced.