When I started watching anime the only way to see series was to buy the VHS tapes or later on the DVDs and I would much rather buy the disks and own the series. The problem is that not all series get a DVD/Blu-ray release so a lot of what I've watched over the past year are just not available to buy.
When it comes to costs, a Crunchyroll subscription is £6 per month and the average price for a Blu-ray complete collection is around £50 so for the cost of one Blu-ray set I get about 8 months of CR. Some of the series I watch on CR I wouldn't want to watch again so I wouldn't buy them. On average I usually watch 2 series a week so far me a CR sub is a really cheap way of watching a whole load of anime.