For the following linear differential equation
most books teach the method of undetermined coefficients, variation of parameters and Laplace transforms. Tenenbaum and Pollard's Ordinary Differential Equations teaches all these methods, but also the inverse operator method and has about 40 pages on it. I have never learned this method as an undergraduate but once I tried to teach it, I loved this method very much and it seems to me that in many cases, this method will be easier to use than other methods.
However, I do not find this method in many books on Differential Equations. Do people generally not teach this method in an undergraduate course? Why?