A JPG stores a grid of colored squares and throws away detail to keep the file small. Zoom in on a logo saved from a website and you will see blocky edges, smudged corners and faint colored halos where two colors meet.
A converter traces those artifacts faithfully, so the "vector" inherits every smudge. We read through the compression to the shape the designer intended, then draw that shape as clean paths with flat colors.
Need the full service overview, with color separation and cutter preparation? See our vector art conversion service. For the difference itself, raster against vector explains why one scales and the other does not.
Don't wait to find a better original. Send the largest version you have now; we redraw from what is visible and ask about anything we can't read.