This is fine, keeping the checklists really simple, for simple planes - as long as all you pilots remember that's what you asked for, when something stops unexpectedly, and you go bump, because you forgot something.
There is no requirement that "simple" aircraft be so common to each other that one list of steps, so simple that you can faultlessly remember them, fits all those planes. There can still be differences worthy of a checklist.
Add to that, modifications, or systems added by STC or avionics changes, which demand extra steps, which may have never entered your memory for later recall.
Also important to note, for slightly more advanced aircraft, the same steps might be presented in a different order, or with variations of event or other steps, depending upon circumstance. I spent 18 hours vetting the checklists, and other Flight Manual aspects for an OEM modification to a light twin known to most here. I took issue with many nuances in the checklists. These are certainly nuances that only the sharpest among us would remember without re-reading. These were certainly not checklists intended for memory.
So, checklist memorizers: You have the indication of an alternator failure in cruise flight, and confirm that indeed, the battery is no longer being charged. You're a while back from a suitable landing area, and otherwise have no need for an immediate landing. Do you extend the landing gear now, or wait 'till you're much more near the destination?
You're smart, and answer: "it depends...." What factors does it depend upon?
You have an engine failure with the fuel pump off. What do you do before you check for selection of a full(er) tank, and turn the fuel pump on? What might you need to open to do it?
I have an aircraft, which has a checklist item which requires that the pilot confirm that the wheels are up for landing. Would you want to do this as a checklist item, or just rely on memory?
Yes, the checklist for the Cessna 150 I have owned for 24 years has not left the seat pocket for... um... 24 years. Except that when I did my commercial flight test, I was told I better produce and use it, or I would be failed there and then.
When being PPC'd on the Caravan last week, I was given memory items to be able to recall, with no opportunity to look for a checklist, when drilled in flight. But, I would have failed the PPC, had I not referred to the checklist at the appropriate occasions.
Don't get in the habit of abandoning the checklist completely, another pilot with whom you fly one day is going to object, and you insurance company might not be keen either....