I presume it's to make sure that only hose people with tickets get in should the card readers not be working. By insisting that you bring the paper version as well, in the event of that happening they'll just rip the appropriate voucher out of your book. If you don't have your book with you then it's your own fault as we've been told several times that we must bring both to the Halton Stadium to ensure entry! This will stop unscrupulous people passing their seasoncards on to their mates and saying the reader isn't working/ recognizing my card.

But if you enter the ground without leaving a trail of some kind, how do they know how many people have entered the ground?

never seen those little hand counters bouncers use?

Nope. Do Saints use them too?

By law, all Stadia now have to have some sort of turnstile monitor counting how many times they admit someone (probably brought in after the Taylor report).

Where I work, the electronic counter is displayed in the Boardroom so the directors can keep an eye on the attendance.

I've no idea, I presume there is some other way, possibly a mechanism within the turnstile. Other sports grounds have these kind of entry systems without the need for a ticket book at every match.

If it is due to possible failure they won't have turnstile operatives on every turnstile, so as Saint Simon says, a steward with a counter (which cost about a fiver) being shown your card is just as easy, if not easier.