I am most probably talking bs here since i haven't tried game as yet, however, predetermined lines / highways if not practically then psychologically feel limiting in wide open space...
Wouldn't have been better if we can draw that lines ourselves and therefore decide which way and how to move with what units!?!?!?
Well, how and with what units you can decide.. just the "where to" is predetermined. Hopefully once I'm done with the colony management answer below you'll understand better why phase lanes are good

Without them, expansion and territory become a lot less important, as your first target would pretty much always be the homeworld so that becomes meh

Can you tell us more about manging your planetary colonies - do you need to feed them, defend them, pay them, will they revolt (ala Total War) if you don't etc...
In short - forget about military aspect and speak about civilian as much as you can
Colony management isn't quite that delicate. Planets have infrastructure (what's bombarded to destroy the enemy colony on a planet so you can re-colonize), population (what pays taxes and gives you $$$), and "allegiance".
Infrastructure is pretty straight forward. Destroy it and wipe out the enemy colony and you can (usually) put your own. Same thing for your opponent! The TEC have a planetary shield generator that reduces bombardment damage while the shield is working, making their planets with the shield generator tougher to take down - if you don't destroy the generator, of course.
Population/planet roles - different planet types offer different max population numbers, which is pretty standard. Terran-class planets of course have the highest, while Asteroids, Volcanic, and Ice have some of the lowest. The higher the population, the more money the planet generates for your glorious empire. Of course, there are technologies you can research to increase the maximum populations allowed on some planet types. Each planet type generally plays a role, too. Terran planets are going to be your main money makers because they support huge populations, and are generally well rounded. Volcanics currently give you a lot of extra fleet points to work with (though it was mentioned that the fleet point system is changed so I don't know what they will do in release). Ice planets are primary crystal resource generators (needed mainly for research and specialized higher end units). Desert planets offer you lots and lots of logistics slots to work with (explained later). Asteroids are your basic outposts, can't do too much with them but they are useful to expand and cheap to manage, and can still support a decent amount of orbital construction/defenses. Dead asteroids are your military choke points - nothing civic can be built around them, only military defenses.
Allegiance - Generally, the farther away a planet is from your homeworld (counted by the number of phase jumps) the less loyal it is, so the less resources it produces (and the fewer fleet points it grants, but as I mentioned that's changing per dev posts, so I'll omit fleet point related stuff from here on out). You can research/build culture centers around your planets to spread your influence to beef up your planets' allegiance for some extra resources out of them, but it's still going to decrease the farther away they are from the homeworld (making good placement of your homeworld - as you can designate which planet you want to be the capital of your empire - an advanced strategy in bigger maps to maximise your resource income). The homeworld/capital itself gets a massive loyalty/allegiance bonus. At the start of the game, it makes something like 10/11 credits/s, compared to planets you colonize making a measly 1-2. Now imagine small maps without phase lanes, and you can see why everyone would just attack the homeworld and cripple the opponent

Orbital building/upgrades - each planet colony generally has some upgrades available: population, logistics, military, exploration, and "make capital" type. All pretty straight forward. Logistics allows you to place more civvy buildings in orbit - things like research labs, shipyards, trade stations, culture centers, etc. Military allows you to place more defenses - fightercraft hangars, cannons/launchers, phase jump inhibitors, planetary shields, repair stations, etc. Some of the specialty military buildings are race specific. The TEC get the planetary shield, while the Vasari get phase gates, building that messes with enemy weapons, etc

Well, that was a long enough essay! I might've missed something, but probably not