Exactly the point. To win, they need to cross all the Ts you mention. OTOH, they can also win if the defendant no-shows.
At the bottom end of the debt collection pool, one strategy is to buy debt with a high chance of no-show and win cases that way... no need for meticulous and expensive lawyering. If people aren't answering their phones or opening any official looking mail...
It's not the only strategy, but it is one.
I think it's a mistake to look at these things too moralistically though. At an individual case level, maybe you're right. It is on you.
What we're looking at here though is an industry. It is built on knowledge about how certain people behave under stress of debt and exploits it. It's also dirty all the way down. Mostly, by the time these go to court the debt has been resold multiple times at small fractions of face value. Crazy interest has been applied.
Economically, it is really going for the last drop. Companies selling off bad debt... it's a pretty marginal income. On the other side, these collection agency debts basically eject a decent portion of the population from good standing in society. It's harmful, and it is happening in a court.
Scale, circumstance... when it gets this big we need to look at it systemically.