even when machine quilting, the higher the thread count, the more tightly it's woven. when the weave is very tight, the needle tends to puncture the fabric so it's breaking the fibre at that spot. the fabric is weakened right there. so if you stitch in a line, you're puncturing holes every place a needle goes through.
if you want to use bedding, look for a low thread count. usually, the less expensive sheets.