[spzb]

The burden of proof falls on the person making the assertion. Why should anyone else have to do the work that he/she/they didn't bother with?

[giantg2]

"Why should anyone else have to do the work that he/she/they didn't bother with?"

Because they are curious (consistent with the culture of this site). They would also be more likely to trust their own sources, I assume.

[spzb]

Trusting sources because they are your "own" is just asking for bias to be ingrained.

[giantg2]

Yet it's well known that if you want someone to change their mind it's most likely to occur if they think it's their own idea/doing. You're more likely to argue with me than if you just read sources you found and independently came to the conclusion.