I think it's more of them passing the buck onto you.
They had to get their file from somewhere... Likely from a client, and it's all they had. They don't possess the skills needed to get it to look good... So they hire out to someone who they think should have the skills.
They might not care if it's accurate, they just want "good enough" so they can also it on a sign and be done with it.
An analogy is kind of hard. I'd say if it was in person (I imagine 90% of your clientele isn't) ask them to trace something while wearing, or not wearing glasses.
Usually we tell the client while their logo is bad quality, they have two options - we can print it as is... We show them what it looks like at full size, zoomed into 100%.. or we can do our best to trace it, odds are it isn't going to look perfect, but we'll do our best.
You've vectorized thousands of items. You could look, and interpret the shitties quality gif, and likely make the trace look pretty decent.