In your game is travel a journey or a hassle?
In a kinder, or more extended way, is the journey, the trip, the PCs are taking a part of the game where what they do along the way is a thing with effort or is it just something to get through in order to get back to the real game?
It's ok whichever way you answer that by the way. In my own games - for literal decades - I never thought of the trip between two points as anything more than just something that had to be done. If I was running a game like D&D, I'd roll for random encounters and other hazards on the way, but otherwise I'd be just as prone to hand wave the whole thing with a simple "it takes you 5 days of travel."
This amuses me considering how much of my own advice to myself has been that it is ok to slow down and really enjoy the moments that happen in the game. There's no rush to get to the next big plot item. The campaign is not a race. Really, unless you have to do something by a certain time - i.e. you're running a game at College and everyone leaves mid May giving you 3 sessions to wrap up this adventure - it's ok to slow down and indulge. In fact, your game could be better than it.
So why did traveling escape me?
Well, for one, it's part of who I am. I'm not the kind of person to go off exploring in real life. To the point I couldn't tell you what restaurants or shops are in the town center not 5 minutes up the road from me. I flat out never really thought about it. It was just "we want to get to X location for Y reason, and to do that we have to travel Z miles." And put like that, why would you even consider that the Z miles could be as meaningful to the game?
And it turns out quite a lot.
The Lord of the Rings 5e books talk about how the 'Journey' the venturing out into the wilds is an adventure into itself. Complete with modified rules to make it something for the PCs to pay attention to, while also pointing out all the ways this can help your game. Further conversation with a friend, and some recent real life experience, fills the rest.
By focusing on the journey you can do a lot of good. A few examples being:
Give The Players A Chance To Express Their Character
Indulging in the journey gives players a chance to express their character when the action of the adventure isn't on full bore. What does being at camp look like for the group? Where do people sleep? Who cooks? What does the morning look like? Is anyone a late sleeper? A light sleeper?
If you are doing a more sci-fi or modern game with vehicles, who is prone to breaking off and exploring the local towns and municipalities or planets that you come across?
Does someone collect souvenirs? Are there neat sights to see along the way? Speaking of...
A Real Chance To World Build
Having big cities and stuff is cool and all, but if you want to sell your world you also need to sell the space between those destinations. The wilderness, plants, weather, natural wonders to see, people to interact with, these are all ways to build your world. If most of your game takes place in cities, the traveling gives you a chance to contrast all the established facts with how life is different out in the country, or on the road.
You can sell how dangerous the wilds are with how other people talk about and do their travel. In fact, this can be better than just having random encounters. A random goblin attack at night on the PCs camp is one thing. Seeing every traveler on the road going in groups complete with armed guards to keep them safe? That can do a lot more to sell the danger of what is going on.
'Side' Quests and Other Encounters
Journeys also give you a real chance to bring in side quests, personal items, and all sorts of other - combat and non-combat - encounters. It can let you challenge PCs in small, interesting ways to go along with the larger ways that the main plot and events do. It can let you show the change in NPCs, or highlight changes in PCs.
You can also have small moments, or even try to foreshadow things. A deer watching the PCs then scampering off is a nice descriptive detail. That same deer being found dead later on can be a warning. And if it died in flight from a perceived danger that sent it into the real danger, you can establish that theme before trying to spring it on the PCs themselves. Maybe they'll notice. Maybe they won't. Subconsciously most will probably pick up on it selling the feel even more.