Two, you had to buy the equipment. Three, the chances that your equipment would be compatible with future services was practically zero. Lack of standardization kept prices high and consumer confidence low. Cable companies decided to regroup. Symmetrical modes, with the same data rate in both directions, are considered too inefficient for home use and are targeted towards business WAN applications.
Cable modems can offer both modes, although symmetrical mode is more common.
Users will notice a big difference when transferring files to friends, sending video or audio via email, or backing up data via the Internet. On and off ADSL service is always on. With ISDN, for example, the adapter is powered by an external device. If your electrical utilities are interrupted, you can't place phone calls over your ISDN line. ADSL, on the other hand, is always connected to the local telco and co-exists with the plain old telephone service that we're all used to depending on in storms, blizzards, and natural disasters.