Very sad to hear stories about retired folks funds being eroded/destroyed by careless (bordering on negligent) IA's. For anyone with basic knowledge they are better off self-managing. Especially in this era of low fee online broking.
Some cases where IA's might come in useful is when there is a lack of confidence/high stress level (so the person needs a "professional" view, or just to rubber stamp what they are going to do anyway but with peace of mind), or to help facilitate a compromise when husband/wife have completely different ideas and risk appetites. But in these cases I would still recommend a fixed fee, advice only set-up. After you take the advice then make your own decision and implement the investments yourself so you don't give away all those fees and trailing commissions.
Definitely it can sum to a huge number over the years if you add up all those compounded fees. Unfortunately many people struggle with their day-to-day finances, let alone retirement planning for the future!