True about loans. Inflation benefits all debtors, not just the government. So poorer people who borrow benefit from inflation more than rich people who lend. As others have said, stagnant wages are the real problem.
Regarding deflation, people living in deflation actually do delay purchases. That's why the deflation persists. There is a cycle that happens where delayed purchases reduce business sales, which causes layoffs. That causes people to delay more purchases.
In your truck example, someone would definitely delay that purchase if they lost their job.