why do people put "begging bowl" links in signatures. You've got a much higher chance of winning a lottery than anyone ever giving you something. If you turned up at my door saying "donate cash to me" what response do you think you'd get?

This is off topic, but I'll address it.
In the early days of Bitcoin, it was common for people with multiple thousands of BTC to flip through forum threads and give 100BTC each to random people thanks to their addresses in their signatures.
Yes, things have changed a lot since then.