That wasn't the point I was aiming to make...I was suggesting that a weekly season ticket will not cause you hassle provided you just carry the photocard with you! Stick it in your wallet and it will always be there when you need it.
The reason you need it is because otherwise the tickets may get passed around and used by more than one person. Some countries do have transferrable season tickets, of course, but the UK doesn't (and you do get safeguards in return for that, e.g. an Anytime (Day) Return being refundable once a year if you have to buy one because you forgot your season ticket and noticed before boarding, though I forget if this benefit applies to weeklies or not).
Neil