How is svg implemented with a background (general plan, for example)?

Question

Canvas

Hello! I have never encountered this and I cannot understand the logic of the implementation of the master plan on the site.
It turns out that a beautiful picture is drawn and uploaded to jpg, then we import the picture in a vector editor and start drawing the layout of each house from above (pixel by pixel) assigning a unique object id. Then we delete this background image and export svg
And on the site itself, we combine the background with the svg image.
So what?
I would be very grateful for advice and opinions.