Because they make a Biblical NEDER נדר with GOD via Holy Land Man. The deal is binding and the consequences of not holding your end of the NEDER with GOD are very harsh.
Normally is something called "ma-eser מעשר" meaning 10% of your "benefit" which you donate to the nonprofit code2GOD to be used for good Biblical causes and glorifying GOD and his name.
If you don't fully 100% believe in GOD, you should not enter the deal of NEDER because once you did, you are obligated to GOD to act according to your promise and deal. The NEDER can't be enforced in court. GOD punishes as he sees fit. It's mentioned in the Bible that GOD states that the punishment is painful 7 folds.
It's like an application with high chances but it 80% of it is up to you: #1 you must have 100% faith and trust in GOD #2 Be visually very clear of what you want. Be able to draw a picture of your wish as if it already exists #3 Make your best offer to GOD #4 Pursue that NEDER as if you're on your own #5 As soon as you start seeing results, start "paying" your promise to GOD. DO NOT TEST HIM!
While NEDER is actually a deal with GOD in exchange for you giving back, you can also ask GOD for a charity act on his behalf and offer him nothing in return. It's called prayer. NEDER has much higher chance to succeed and become a reality.