HC's have "normal CMOS" input thresholds halfway between GND and VCC, and unambigious range between about 30% and 70% of Vcc (slightly depending on the part, of course). I.e., when powered from 5V, to get "zero", you need to input < 1.5V, and to get "one", you need to input > 3.5V. The latter requirement makes it unusable for level conversion from 3.3V, as you'd need at least 3.5V input signal for reliable "one". So it typically works only by luck on the lab table until you put ten units on the field...
HCT parts, on the other hand, offer so-called TTL levels (one of the most misused terms ever, so now we are talking about the correct definition) on their inputs, which means they guarantee that anything over 2.4V is interpreted as "one", even with a 5V supply. That's why you can use a 74HCT buffer (or any other gate) to do a level conversion from a 3.3V to 5V.
Fancier level conversion parts exist, but if it's just unidirectional 3V3 output to 5V on a logic PCB, a HCT buffer is a good solution.