Additionally fifth days can be great for spectators. See a guaranteed victory for knock down price that will probably last no longer than a session. They're good days for kids, getting in on cut price tickets or even free, to be introduced to test cricket at a duration to hold their attention spans. It is also affordable for people who may have been priced out of the full price tickets, or couldn't obtain tickets, for days 1, 2, 3. The atmosphere is more relaxing, being able to select your seat, more akin to a county cricket match. There is a lot of joy to be had about a fifth day on a test match.
Further, it is not as if the attendances for fifth days are that bad. They are good at The Oval and Lord's, or even 'Oop North if it is The Ashes. The British love their Test cricket and the fifth day certainly has a place in that. The Sri Lanka Test on the 1st day at Chester-le-Street - I repeat the 1st day - was attended by 'one man and his dog' and Headingley was not much better so it is not as if fifth days are part of the problem per se, more the quality of opposition, awareness/interest of the sport (proliferation on television/competition with premiership football), ticket pricing.
For god's sake. The sport has been tampered and changed with. We've seen the introduction of gormless Twenty20 plastic cricket, pink ball night nonsense and all sorts of tinkering and stupidity. Keep one thing sacred in the greatest format of the sport: the epic nature of the five day test.