How many members have been removed from internet cycling vendors, only for having inactive accounts?
As the account has reliable payment history.
Who has done the removal? As many don't ask, at least to me, if the account is inactive -- because of any possible customer service dissatisfaction. Maybe the customer has other priorities that must be paid for, first. As the customer wishes to continue business with the vendor. There are those vendors that claim cost involved, for sending emails --- as inactive customers are a waste of their expense.
As others say "There is no cost to this."

There IS a financial and time cost attached to administering and sending to inactive accounts.

But to answer the original question. No, I haven't been deleted from mailing lists or having an account with an on-line vendor. I keep active with at least one purchase a year from most, such as CRC, Wiggle, CyclingDeal, Pushys, Torpedo7 and so on. But even with Gound Effect, from whom I have made just one purchase, I still get their e-newsletters.

As to reasons why someone's name would be removed apart from inactivity...if criticism is always at the top of a person's agenda, and they want to complain about everything even though most other reasonable people wouldn't (and wanting something for nothing tops it all), then I think that as a business operator, removal as a discouragement to continue as a customer would be a wise thing to do.

I am assuming once your email is registered into the vendor's database then it would be more work to actually remove it yea? Since same email/pdf is sent to all accounts at once.

Methinks Mr. Molten complains too much. Wait . . . did anyone else detect the scent of 'troll' when they opened this thread?

meh, just another rant about something no one cares about...

Just return to their site and opt-in again. There's a couple of reasons for a vender to do this.

It's not no-cost. You can set it all up on your own, but your own smtp server won't be white-listed and most of your emails will bounce. Otherwise, sending thousands or tens of thousands will cost you something.

More importantly if you're getting a number of spam complaints (rightly or wrong) you risk running afoul of CAN-SPAM and it would be easier and safest to just reset the list to current customers.

Ribble upgraded their website a while back and made everyone make new accounts. I think the mailing list is only harvested from that and becomes separate, though, since there was no pause.