Just because they want to spend on batteries doesn't necessarily mean they can spend on power lines. Most of the time you can't just pay the power company to bulk up your lines, just like you can't always pay an ISP to install a faster connection, even if they provide that service to another area.
Okay but that's a completely different objection from the one in your previous comment.
And yes it's not always possible but it'll be available in enough places.
If a particular station can't get better lines, then as someone else said they could have fewer charging spots. High load per spot still works out well for them, because they can save space.
