oric, he's not referring to just the pads, but the entire board. Not everyone get their boards professionally made. Those who do it at home end up with bare boards with exposed copper traces just like Jack's picture. Depending on the environment, the copper will tarnish over time. While that doesn't affect the solder joints already made, it just makes for an ugly looking board over time. This is where the coating comes in helpful.
On the contrary a lacquer coating will protect against dirt and grime building up (which in humid conditions will conduct).
How are you gonna plug something in if the connectorpins are coated? [snip] .. so who cares what it looks like later on. What's important ishaving good connections.[snip] Fourthly, it's lots easier to buy professionally made pcbs and then the pads are always pre-tinned in the first place.
(note to self - must remember to etch her a message on the PCB somewhere too, chicks love that sorta thing)