Those filters were used for analogue signals. As far as I know, they didn't affect the (most?) digital signals/frequencies, hence encryption is required. Yes, now that they use encryption, it eliminates cable theft and eliminates a huge number of truck rolls, especially for programming changes. With a-la-carte on the way, it's become a necessity since all channel selection will be handled remotely. Also with STBs the provider can do a lot of diagnosis of signal remotely, etc.
Most providers never bothered with a truck roll to install a filter because they hoped the user would re-subscribe to cable TV - it just wasn't worth their while to make the trip. I'm not sure why it took Cogeco so long to encrypt. Satellite and IPTV has always been encrypted and most cable companies have been encrypted (at least above basic) for years.
Most providers now have a minimum of analogue channels with some providers now totally digital.