If your parents helped with the planning process (either financially, or maybe they helped put together centerpieces, or went dress shopping/looking at venues/etc with you, or talked with you whenever things got stressful during planning, etc), many people get them gifts to say thank you. I don't think it's required, but it's a really nice gesture, especially if they helped you during the wedding planning process. If they didn't help, people sometimes get gifts for parents that state something along the lines of, "Thank you for raising my future [husband/wife]", to start their married life off on the right foot with each other's family.
Wedding sites and the gifts industry ads and articles have been pushing gifts to everyone, and thank yous to people who should be thanking you, by way of suggesting good gifts for parents, or your vendors, or proposals to ladies, anything to get you to spend money on them. Their business. But parent gifts have never been traditional at wedding time, beyond the photos given them after the wedding, usually in an album, or framed. Other than that, at weddings, parents should give you a gift, which for many includes financial help with the wedding. This they should be thanked for, in writing, gift or money. But standard etiquette says when someone gives you financial help for a purpose, or a gift, you do not thank them with a gift ( thus giving them back a gift they essentially paid for.) Weddings, or any other occasions. ... Mothers Day, Fathers Day, birthdays, their anniversary, and gifts for any holidays you celebrate ARE traditional gift giving to parents occasions.
I made a wedding album and a canvas print for each set after the wedding. We didn’t give them anything the day of. We were also going to take my parents out for dinner as a thank you since they helped pay, but they wanted nothing of it and changed the subject when I brought it up
We got individual gifts for each parent. I got my mom a collage with photos of me, my siblings, my dad and her since I was a baby to the present. I got my dad black socks that said special socks for a special walk and a travel mug since he uses one every day for work. My husband made an album of photos from a trip to Alaska him, his dad and his brother went on a few weeks before the wedding. We gave his mom a framed engagement photo. The photo was taken at the park she was a ranger at for 19 years, were we got engaged, and in front of the tree she planted in honor of her dad when he passed away.
I got my mom a personalized handkerchief and a box for jewelry/other special items. I got my dad a photo frame with an IOU for a picture of him escorting me down the aisle. We got our families parent albums for Christmas that year.
My dad has a secret love of elephants, and we found a gorgeous little paperweight at the zoo. He likes to work with his windows open, so we got that, and then I found an old childhood pic of the two of us, so I threw that in.
My stepmother "requested" something very specific from DH's job (a reuseable water bottle, actually!), so we kept our eyes peeled, and grabbed one when it showed up!
For my ILs, we ended up giving them a triptych picture at Christmas.
As others have said, they're optional. They don't have to be expensive. If you think about getting them something like a birthday gift, that'll work.