Because you have much more choice for VPN providers than for ISPs. And you can change VPN periodically, far more easily than changing ISP. Also, you can use nested chains of VPNs, much like Tor, to distribute trust. So adversaries must compromise multiple providers, quickly enough that logs will be available.
Edit: Also, you can pick VPN providers outside your adversary's sphere of influence. That's standard advice for users in China, for example.
Also, you can pay for a VPN without revealing your identity. Not so with ISPs. I use a VPN, for instance, to mask my Tor usage from my ISP. (I'm an American using the Internet in the United States.)
True. But the VPN provider effectively knows who you are, because they see your IP address. Or rather, a resourceful adversary can get your IP address from the VPN provider, and then get your identity from your ISP.
If you chain VPNs, however, it certainly makes sense to lease the second/indirect VPN anonymously.
I don't think IP alone will not be sufficient, for ex i am sure my ISP extensibly NATs the network and shares the same IP for many users. So much so that Google keeps asking for captcha every couple of days
And now both of your vpn owners have your data connected to your ips. You do have more choice but if both of them sell the data, it doesn't make any difference.
I've lived places where my only ISP choice was Comcast. I trust them as little as the worst VPNs, and having a choice of VPN lets you choose one which is trustworthy and in a convenient jurisdiction. That matters some in the States (no NSL to Canada, for instance) and a great deal in China or other countries.
Yes, it is unfortunate. But hey, you gotta deal with what's so.
There is a learning curve, and extra steps in configuring a working environment. But once the host and VMs are configured, uptime is no worse than with typical LANs.