Both being monstrous liars makes no sense

Why do they both lie excessiveli and unnecessarily? I don't condone lying, of course, regardless of the situation, if no one is in actual physical danger (or some other similar extreme situation that I can't think about right now), or at least exists in a mega-fearful, terrified state (still not OK, but understandable and I can give it a pass - I might lie if I fear enough as well, although I have been honest almost to 'test the Universe' in situations where it's 100% obvious telling the truth will land me in a lot of trouble - and somehow, I didn't end up in trouble, so truth shall set you free!)

I am going to write an example from both - please realize, these situations in NO WAY prompt, necessitate or 'need' for them to lie. They don't benefit AT ALL from lying, they would not gain a problem by telling the truth, and yet they both lie. Inexcusable!

Neal Page: 'I hailed a cab at..blahblah'

Did you, Neal? Did Neal really hail that cab? OR! Was it like we were shown; an attourney hailed the cab and Neal went to negotiate with him, and ended up paying 75 dollars for the privilege of having it (or more factually, for the attourney to NOT take it).

Why does he say HE hailed it, and doesn't even mention the money exchange, which would actually make his point even more.. well, poignant?

This makes no sense.

Del Griffith: 'Oh, we almost hit a deer, that's all'.

Did you, Del? Did you just almost hit a deer? Absolutely NOT! Why couldn't he simply tell the truth? He had trouble with his jacket/parka/whatever getting stuck, and he decided to, instead of making the rational choice of slowing down and stopping safely and then deal with the problem easily, keep driving at a high speed until he was going to hit a stop sign / curb / the edge of the road / etc.?

Why can't he have said 'Oh, I just had some jacket trouble that caused me to drive recklessly, because I don't like to stop in these life-or-death situations', I am THAT unsafe a driv...

..hmm.. ok, maybe Del's life makes a LITTLE bit of sense, but it's still a lie. Maybe Neal would not have let him drive after that - WHICH, however, could only have BENEFITED both, because then 1) Maybe they'd notice the heavy cigarette smoke coming from the back seat and 2) Not wreck most of the car by driving in the middle of two maniac psycho truck drivers that know how to honk, but not how to slow down or stop (just like Del.. what is with movies and drivers not thinking to slow down or stop? Watch almost any movie where someone is almost run over by a truck or train (Stand By Me, Ahem!), and you can see it makes no sense for the engineer/driver to even TRY to slow down/stop.

3) So the car would be fine, and they would not be stopped by the cop, because they could drive responsibly and follow/obey the speed limits

4) So they could get to Chicago faster, more efficiently, more comfortably, and with the heater probably still working.

So telling the truth, again, would've made their trip about 200 times more pleasant for BOTH, mind you.

Tell me again, WHAT was the benefit of them lying, again??

Makes no friggin' sense.