I think cost comes into it. The cheapish (£165 .62 delivered including a charger) 15Ah Yose silverfish battery that I bought in March this year is working well and hopefully of decent enough quality not to be a fire risk. It lives on one of my rear hub bikes in my attached garage and is charged there using a timer plug. I do set the plug to the maximum time it has which is 8 hours to allow for balancing. I also tend to use the bike the following day so that it does not sit there fully charged too long. But that is basically it on my battery care.
I have had a previous Yose battery that has lost some capacity but not that much and is over four years old so I am hoping this newer one will be similar. I even have the original silverfish battery that came with the rear hub bike that I bought for £100 from the clasified section of pedelec, and that still works and dates from 2011.
Less capacity of course but I did use it to ride 10 miles to work on full assist on a bike that assisted to 20mph carrying sadly over 100kg of me and two full panniers. I could charge it at work so it was full for the return trip. I guess what I am saying is if the batteries are less expensive you are less worried about how you look after them. The benefit is that the bike is ready to use without any pre ride battery charging planning.
The Yamaha battery on my Haibike is available for me to buy from the shop where I bought my bike but only the more expensive larger 500Wh battery priced at £849.99. My whole bike cost £1,750 to put that price into perspective and does not include a charger. If you needed a charger that would leave you only a couple of pence change from a thousand pounds.
As a consequence I do my best to look after my original 400Wh battery. But this really only entails bringing the battery into the house after a ride. Storing at 50+%, and only charging it back to full as close to riding the bike as possible.
At some point when I was using my bike very regularly to commute to work and having read that lithium batteries lasted longer if you charged them to around 80% rather than full, I made a few trips to work with a not quite full battery, but it would then be charged back to full at work. However Nealh pointed out that ebike batteries are different to electric car batteries and it was better to fully charge the battery each time so that the cells balanced. So I reverted to this but tried only to charge it close to when I planned to use it. This means that using the Haibike involves some forethought and planning which means it can be not available when you suddenly want to use it or conversely very occasionally has a full battery and your plans change and it does not get used. In those circumstances I take it out as soon as I can, generally the same day and ride it up and down a steep hill to take the edge of the battery.
There is none of this fluffing around with my ever available rear hub bikes.
However the Yamaha battery cared for in this way is lasting extremely well (Thank goodness) with still good capacity and working very well. I don't tend to ride less than about 20 miles and do use the higher middle assist to blast up the last steep hill home and am usually still above (just) 50% capacity left when I get home.
I meant to say that The Yamaha Battery is 7 years and 9 months old and my bikes total mileage to date is 16,774. Thank you the other useful replies, I will try and comment when I have more time.