(Please ignore my huge forehead. lol!)
Actually, if people have not suffered any hair loss issues from chemicals or mechanical damage, etc - then I do not think they are going to get any thicker in density by starting locks. Typically, if people discontinue anything that is causing damage, then their hair naturally starts to grow back where they lost it. It is that simple.
So I have come a long way in an 11 months span, and I personally can tell that as my locks get longer, I will probably just wear them straight. The daily hydration spraying is going to prevent my sets from holding.
So if you are suffering hair loss? Then starting dreadlocks may be an answer if you do not have permanent scalp scarring.
If you have a thick head of hair, then dreadlocks will not make it thicker, but you will have some huge, big hairstyling if you start rolling it. So you may have less styling options, but for me, I've had 40+ years of styling options. I was ready for micro-locks. I can tuck my locks under a wig if I need a different look, but each one to one's own.