Having refurbished quite a number of machines the one thing I've noticed is that not all machine sew straight. Some want to twist the fabric, some will gradually move it to one side or another, and some that are really out of adjustment or worn will try to rotate it.
If this happens a visual guide is all but useless. The sewist is fighting a mechanical problem that needs addressed. I have adjusted the alignment of the foot to the feed dogs on so many machines I've lost count. Most can be adjusted to sew straight, some simply will not cooperate.
Sometimes you even have to replace the foot even if it looks OK.
You may even have to replace the feed dogs if they are worn.
If you have a machine that is mechanically redirecting the fabric, you have to manually guide it every stitch. That gets tiring as you can't keep a straight stitch that way.
If the machine sews a little off then a physical barrier type guide might help at this point. And since there are so very many different kinds I fail to see the logic is wasting the time building up a wall of sticky tape on the bed of the machine.
If you want, take a strip of fabric about 3" wide, iron it flat, and start it with the presser foot centered. If it sews straight without being forced, then you and your machine is good to go. If not, then get the foot / feed dog problem fixed and sewing straight will be a lot easier.
Joe