Do you need a sewing machine if you have an overlock machine?

Yes, you still need a sewing machine, as the overlock machine is designed simply to finish the edges of the fabric. Overlock machines do not go backwards, turn, zigzag, or anything stitch functions that you may need (depending on what you are sewing)
You do not absolutely need a sewing machine if it's a quick and easy project (such as a repair, or a pillow), but for everyday use, you need both.
Yes, you still need a sewing machine, as the overlock machine is designed simply to finish the edges of the fabric. Overlock machines do not go backwards, turn, zigzag, or anything stitch functions that you may need (depending on what you are sewing)
You do not absolutely need a sewing machine if it's a quick and easy project (such as a repair, or a pillow), but for everyday use, you need both.