Why are companies spending fortunes on short, memorable, brandable domain names?

Short easy to remember, distinct in ads, easy to communicate by phone, less typos

Memorable 2h may mean many things, Hon Hai precision industries (Foxconn who produces products for Apple), Hilton Hotels, 2H offshore, love flowers in Chinese (or many other meanings).

Brandable just a few trademarks registered in some countries

How do I know that the domain has not been used for porn, gambling or other fishy web sites. This domain has only been used for my own web site about online personality and IQ tests, for a period I was number 1 on Google, but then the algorithms changes so it dropped and I did not have time for serious SEO. You can confirm the history on archive.org.

What is a reasonable price for this domain? Looking at the history of publicly available domain sales prices short domain are among the most valuable. For the right buyer a short domain may earn its price many times over in savigs on advertising, brand value and saved advertising. For the right buyer the domain could well be worth a six figure USD amount.