Why can’t you just do mazes?

So confused. Husband and I booked the foursome ticket as we only wanted to do the mazes. We arrived and they wouldn’t let us enter as we needed a fright night entry ticket???? So why are the mazes tickets even sold separately as we could have just paid the £70 ticket and got on with it. Instead we had to book an entrance ticket then and there which was £64 each!!!! So we paid around £100 each!!!!