Yes, if one needs some advanced feature of a DAM then one needs a DAM.
But the way many non-pros look for their images they could achieve the same result 95% of the time by simply using the tools available in their operating system. If it's in the metadata you can search for it (lens type, check; focal length,check; keywords, check; geotag, check;...). In fact you can search for those files the exact same way from any 'open file' menu of ANY program on ANY computer: your Raw Converter of Choice, check; PS, check; RawDigger, check; Microsoft Office, check; ... When I tried LR a couple of years ago its DAM did very little that I couldn't already do and in fact it put major constraints on what I could do and was used to doing. Did I mention that I use one of three computers at any one time plus NAS?
So what do you, the average low volume/high IQ non-pro, really need a DAM for? Good question. If you know the answer to it then you are probably a good candidate for a DAM. Hans knows and he is a pro. Otherwise you may not need a dedicated DAM at all, the advanced search tools built into our operating systems will find image files just fine. In that case choose the raw converter independently of its DAM capabilities, based on how easy/good it is at converting raws into rendered images. LR favors speed and convenience, sometimes at the expense of quality. Others make different compromises. To each their own.
Jack
Manoli is correct, a well thought out folder system is the basis of efficient image storage in the long run. On the other hand from the user's perspective folder structure is independent of the search capabilities discussed in this subthread (via dedicated DAM or OS). Throw all images in a single folder or create a folder for every image if you prefer, it works the same.