VOIP over the cable system (i.e. Cogeco/Rogers) is prone to outages due to blackouts even if they don't occur in your neighbourhood.
Cable system amplifiers are tapped into hydro at various points along the way to your house.
If the hydro goes out a few blocks over and your neighbourhood is fed from that area, out goes your phone, internet and TV.
Landlines are self powered and backed up with batteries/generators.
Cell phones are fine and all, but good luck for the security system.
Agreed, the landline infrastructure has the advantages you've listed. For those who want protection from power outages and still have the possibility of phone service then a landline may be worth the cost.
Its not an either or situation. You can have VoIP, Cell, Skype, Google Voice, etc for daily use and landline for backup.