Where the analogy fails is that being able to upgrade a computer can well increase it's lifespan more than it would a car. People don't generally need faster and faster cars each year to keep using the roads in the same way they might with a computer.

When I was a teenager I made reasonable pocket money upgrading peoples computers from 16 to 32/64MB of RAM because it saved quite a bit vs the cost of buying a whole new computer and made a significant difference when running Windows 98.