You Light Up My Life was #1 in late 1977 (number one for 10 weeks I might add, based on airplay and sales)...If 18 year olds girls were buying her 45 record that year, they'd be 54 today. 70+ is stretching it, don't you think? I highly doubt just 30 and 40 year olds were scooping up her records that fall.
As for Lou Rawls, heck it's on the CBS-FM and KRTH playlists, so they are appealing to the under 54 crowd, not 70+.
You want 70+, try early Dionne Warwick or Sergio Mendes classics, as good as they are.
Oldies, you really have to get your brain around the concept of "appealed largely to" versus "just 30 and 40 year olds".
Yes, there were younger people buying those records. But the dominant appeal was adults.
Same for Dionne and Sergio...which means those records are likely to be 75 or even 80+ now (I love them, but we've already established I'm weird like that).
So, with Debby Boone and Barry Manilow, you're starting with records that were not universally loved by 15-year-olds then, who'd be 51 now, and on their way out of the demo anyway.
And....and this is something I've spent a year trying to get you to understand....something a 15-year-old girl loved in 1977 is not necessarily something she loves at 51...or even that she still loved at 16 (worth remembering when you run into your high school girlfriend at your next reunion). Especially when it comes to music and fashion, women tend to be more trend-driven than men.
I'll bet you lunch the phrase "that's so last year" was not first uttered by a guy.