My state (NY) doesn't require the CNA to get into an LPN program. Since I was once a CNA, am currently an LPN, and having just graduated from an RN program I think I can give my opinion on this matter.
What I gained from being a CNA was confidence in dealing with residents and patients during my early clinical experiences during LPN school. I also did really well in skills lab when I first started the LPN program, the first 4 weeks were a breeze. However after that the playing field was leveled and my classmates with no prior experience were doing just as well as I was.
If a prospective nursing student wants to become a CNA to get their foot in the door at a hospital or LTC more power to them. It's a good job and if the nurses know you are in a nursing program they may be willing to show you some things that will be helpful to you. The thing is that I don't agree with forcing a person to pay for a CNA course if they have no interest in working as a CNA during nursing school. These courses can cost anywhere from $400 to over $1,000 depending on the school you go to. If you don't intend to use the certificate then that money is wasted because you will learn the CNA skills during the first few weeks of nursing school and you will not need the certificate once you are done with the LPN program. Some states will even allow you to do the state exam for CNA with no further training after you complete your LPN or RN program.