Why is Wikipedia always asking its readers for donations? ?

What's worse is their math, a 'one time event' seems to keep reoccurring. 

they need money

The organization had started a campaign and asking readers for donations to support the website. They have no ads, shareholders, so they ask for donation. 

I was going to donate then found out  

1. They have reserved of over $20m

2. Wiki is valued at $10 billion.

Jimmy Wales will collect a big fat cheque one day , don’t feel you have to add to it.

Well, the information on Wiki doesn't just appear on the Internet by magic. Somebody has to maintain the servers, take care of the software and all of the other stuff necessary to maintain their sites. That's why they ask for money. I get asked by email fairly often. Sometimes i give, sometimes I feel it's time for somebody else to give a little.

Wikipedia is a free source and, of course, to maintain that service, some money are required. Wikipedia because of its philosophy, doesn't want to host advertisements. Of course with private sponsorships it would receive lots of money, but all of that is against its rules. So, Wikipedia is often waiting for private donations from all the users.

'Always' is not true. A couple of times a year, no more, do they ask. It is a free service with no ads and if you use it frequently, you should give a few dollars each year.

They need to pay for the servers that host all that information that is available to you for free. Without donations, Wikipedia wouldn’t exist 

Believe it or not but even Wikipedia needs money to purchase hard drives or SSDs, internet bandwidth, and people to keep an eye on things running as they should do.  None of these things are cheap.

To get money.