As others have pointed out, FTP speed will depend on a lot of other factors. "Not as fast as they could be" is somewhat subjective. Have you timed the transfers, timed the transfers using other methods (i.e. commandline FTP, GUI FTP Client, etc). Keeping everything the same (transfer the same file several times using a particular client app) and average the times and rates. Things outside your control could also be impacting these speeds (time of day, traffic on the networks between you and the client. There may also be some throttling going on between the client and server that you aren't even aware of (I've seen it happen). If at the end of the day, it's something outside of your control, there's nothing you can do about it apart from burning some offerings to appease the network gods :-)

Hope that helps a bit.