Cheaper fabric and/or harsh washing machine and/or harsh detergent.

" Is it because the of the washing machines or the detergents we are using today? "

Not if you're using a front loader, which is much gentler on clothes than top loaders in general, and agitator models in particular.

Part of it is fabric content.
I got some Eddie Bauer T shirts a year or so that are a poly - cotton blend. That may have been how they did the more heather-y colors. These are pilling already.
I have a couple of their T’s from over 10 years ago in 100% cotton that I wear all summer & have no pilling , no holes.

Pilling is, of course, caused by abrasion. Multiple factors can come into play. Fabric quality. Lower water levels in both toploaders and frontloaders causes more friction. The advisory nowadays to reduce detergent dosage, more rinsing to eliminate any trace of suds ... detergent makes the water slippery, reduces fabric friction.

" I have a couple of their T’s from over 10 years ago in 100% cotton "

That Eddie Bauer no longer makes women's t-shirts in 100% cotton has been a huge disappointment for me. It's really hard for me to find 100% cotton T-shirts for women that fit me, and I used to wear tons from Eddie Bauer.

OT

Toronto Veterinarian - I agree re: Eddie Bauer. i have not shopped there in many years after they changed their targeted customer audience, styles, and got away from 100% cotton tops. I still have some old EB cotton tees that are wearing like iron.

I think a lot of it is the quality of the fabrics . I have several very old items, that are almost thread bare and there is no pilling.