★★ ʜᴀᴋᴀɪ ★★
Something that I noticed more now than I did as a kid watching the show is that Goku was and basically still is a terrible father. From the start of Dragon Ball Z, we see this unfold pretty rapidly. He spent a good chunk of Gohan's childhood life dead or AFK which is pretty bad. In the absence of Goku, Gohan still had a parental figure that helped him big time.
Piccolo to me is a stepfather to Gohan. He filled the void for Gohan with all of Goku's absences and even trained him. He grew to care for him pretty early on and him saving Gohan's life during the Vegeta Saga basically cemented that foundation for their relationship. I would argue that Piccolo is even a better father than Vegeta himself.
I think this comes down to the Namekian nature vs the Saiyan nature. Nameks are both protectors and caregivers. They almost fill the role of a mother and father simultaneously. They are also self-reproducing. As for the Saiyans, well... They are brutes. Reproduction to them isn't about bonding or family, it is merely about increasing numbers to their army. Goku didn't have this mindset from the head injury and Vegeta had to unlearn it but still seems to struggle to some level with bonding. He was also the product of an "upper class" bloodline so he has more internal intelligence to him as compared to Goku.
I just find Piccolo and Gohan's relationship to be one the most interesting in the entire franchise since Piccolo wasn't really obligated to do anything and at the time of taking on the parental role for Gohan, he still somewhat hated his father.
This is still one of my favorite scenes: