They are auto traces. Auto traces are often ludicrously inefficient.
I did actually start this the other day, but I just don't have time to be spending hours on other peoples decals at the moment when I've got hundreds of my own to make.. but just to explain...
The image below on the left is an extract from the trace file you made, on the right is as far as I'd got with drawing it.
View attachment 1445931
If I make it just lines, you can see how many lines are in the trace file versus my drawings, there's literally hundreds,
View attachment 1445927
The red squares are nodes, those nodes are mostly what makes the file sizes what they are... there are thousands...
View attachment 1445928
That's why the files sizes are massive.
You can't really get around this using an auto trace.