Certain hair types are naturally more porous than others, also one can do a heck of a lot of damage mechanically, not simply heat or chemicals. My understanding is that part of porosity is the presence or absence of the protective fatty layer on the hair, this can be destroyed by a single hair dye session, UV damage, brushing/ combing, any shampoo soap or alkaline product like baking soda. Sulphates are certainly major culprits but not the only ones, all shampoos are designed to break down lipids.
The canopy can suffer from incidental sun damage, the UV protectants in hair products are low factor and chemical not physical so they need reapplying regularly. Naturally porous or damaged hair will suffer hygral fatigue simply from washing and, according to Komaza Care, also during long deep conditioner sessions. Solutions include wearing a hat every time you are near the sun and consider using coconut oil to reduce porosity and protect from protein loss.
I had tons of breaks all round my hairline and at the back plus progressively increased porosity towards the ends from wearing a ponytail 24/7, brushing it into that style when wet, repeatedly, twirling the ends in my fingers and suchlike. I was using 'no snag' hair elastics and a decent paddle brush with wide spaced teeth not giving myself a 'Croydon facelift' or anything high traction. Nothing like backcombing nor blow frying with a round brush either (so much brushing on vulnerable wet hair if you think about it).
Two years on I'm still chemical treating, but the really horrific porosity and patchy breaks is gone, I've cut back on the mechanical damage and stopped all shampoo (CO-wash). I know the water damage is greater when I shampoo because of how much colour I lose/ retain. The rare time I ponytail now it's super loose with a soft terry towel band or small scrunchie, I wouldn't even dare 'pineapple' without a silk/ satin pillowcase.
Tangling on one side ... where you sleep, car seatbelt?? Good article