Not all power grids deliver constant 230V voltage. Even minor variations in mains voltage will cause undercharging or gassing. Undercharging will result in the negative plate not being fully converted and therefore part of the material will be inactive. Overcharging will cause gassing in the battery which will dry it out and the heat generated will damage the lead plates.
The CTEK range of switched mode battery chargers operate independently of variations in mains voltage which means the batteries are charged efficiently.