I want to open up a discussion that I can’t seem to find a lot about regarding how data are processed for individuals. When using a software like GEE, with lots of data availability and various products readily available, do people tend to do their own corrections or use what is already available? It seems like for convenience’s sake, one should just use what is already available in the catalog. But the staunch programmer may want to know exactly how the data are processed, and have a larger body of data to pull from initially.

For instance, with the raw Landsat 5 imagery catalog in GEE for my study area, there are 195 available images that fit my criteria. When I look at the Surface Reflectance catalog, there are only 104 images available. That results in a gap of nearly a decade in my imagery when using the atmospherically corrected data, but the ease of use makes me curious if doing my own atmospheric corrections is really worth it, and why that gap exists in the first place.
So, the question becomes: In GEE, how are raw images corrected, why is the gap in available imagery so great between TOA, SR, and Raw scenes, and should one consider doing their own corrections to have as much data on hand as possible? I’m curious what others think on this topic. Thanks everyone!