How "necessary" is a license?

Don't wanna start a comment war, I'm planning on getting my license soon. Just had a question regarding urgency.

So I'm a total radio newb, I've had a passing interest in Ham over the years but I never got into it and never had a CB until I bought a jeep to 4x4 in.

Problem is, nobody uses CB in the group I'm going with. My dad told me to buy a "rugged radio" and said that's what everyone uses now, so I just went with that before knowing what gmrs was. Fast forward to now and I'm getting pulled into the hobby side of it all and wish I would've looked into other gmrs equipment. But I digress.

I'm only planning on transmitting when needed out in the woods. As far as I know there's nobody else using the groups channels and nobody runs into interference issues. Realistically, does not having a license matter? My dad had no clue you even needed one and has been using this radio for a few years now, I'm not really worried about an FCC van finding me. I just don't want to cause problems for other users.

Edit: GMRS license is applied for, now I just wait for a callsign! Thanks to all the commenters giving informed advice!