What's that mean to the computer illiterate among us.
Higher latency = slower connection (because reasons)
ISP rerouting traffic or simply forgetting about it = ... well... needs a bit longer.
Unless you *are* an ISP (Internet Service Provider), all your traffic will be going through an ISP. Because provision of service, ISPs will handle different data and requests differently, or cache different data. For example, an ISP doesn't want to go out to Google and grab the Google logo every time a customer requests to go to google.com, so they'll just cache it locally on first request and just update every now and then; far more efficient from the ISP's perspective but you may end up with an old logo between updates. Less common sites, it'll probably just go straight there.
Problem with VPN traffic is it's all encrypted, and it's usually high-volume too, so no value-decision can be made about it. If 90% of VPN traffic is, say, the latest Game of Thrones episode or something, the ISP can't determine that, and so can't cache it. This can cause quality of service problems for some ISPs, so they need to mitigate that by having VPN traffic get rerouted so as to not impact "normal" use.
Think of it like trucks. Trucks *can* go everywhere, but they significantly disturb high-residential density areas, or can cause major congestion in non-major road networks. So trucks are made to take longer routes to avoid those major residential centers and stop those problems occurring, but it means the truck takes longer to get where it needs to.