Yes there CAN be Worms in your Potted Plants

So I am new to gardening and today I learned that worms can crawl into your potted plants outdoors. I was re-potting some succulent plants and found a worm in each pot. One 3.5 gallon pot and one small 3 pint pot. I didn't think there'd be one in the 3 pint pot (I found the first one in the 3.5 gallon). They are on the ground, but above a 2 square feet cement paver that's about 2 inches thick...so there is no direct contact with the soil beneath. They must've crawled on the paver and then into the pots somehow. I didn't remove them...I just let them live there. Just need to remember not to bring the pots back indoors. =) I heard that the holes they make in the soil may let water go straight through the pot instead of soaking the soil for the plants...but these succulents don't need a ton of water so I think it's ok to keep them in there...right? Anyway, I had no idea they would do that with the paver...but then again there's only a paver and then it's all dirt underneath.