For Levitation it makes some degree of sense in general, but it does establish a change to the magical world by doing so.
As a concept, you would need and want to guide your target to the destination, not smack them into beam, light poles, zeppelins, whatever. If you lost LOS, but maintained concentration, they would presumably either just hang in mid air or else continue on the same trajectory you had them on previously. Therefore, you "need LOS" on the spell, but that may only be in the context of moving the target.
SR doesn't have a "Line Of Effect" clause on spellcasting, meaning once cast, nothing can break the effect other than in the case of Limited range spells. If I cast Armor on the street sam, it stays until I drop it. They can be around the corner or around the world. Same with Mask. I have to touch them to cast it, but I don't have to stay in contact. It's just not stated to the contrary.
5E Area spells: "All targets in the area of effect that you can see, friend and foe alike, are valid targets for the spell. If a potential target is outside your vision (behind a screen, for example), they’re not affected." So by this rule, even a fireball that detonates behind a point of cover will not hit targets you know to be hidden behind that cover, because you could not see them at the time of casting. No matter the radius and the fact that the ball of fire will roll over the top of them. This rule also contradicts the "bouncing spell" AoE mechanic elsewhere where AoE spells have scatter for the first time. But I digress.
5E Levitate: "The subject of the spell can be moved anywhere in your line of sight at a movement rate equal to the spell’s Force in meters per Combat Turn." No rules on drops or what happens if you lose LOS.
So, thus you would need LOS to cast it, and LOS to move them. However, 5E does not appear to have a ruling on things otherwise. If a character who was in range and in LOS of a spell at casting, but then moves out of LOS (but stays within range), there's no rule on how to handle that. Conversely however, if a character leaves the range of a Limited spell, they are no longer affected by it. No rule here = it's up to the GM. It would not be unreasonable to say going out of LOS breaks the spell effect. It's consistent with other mechanics.
However, with 6E, the description establishes only a single-case change to the game universe that was never explicitly true in any prior edition:
"The target has to stay in sight if you want them to stay in the air; the minute they’re out of sight, they’ll be earthward bound."
This implies but in no way can be confirmed that the same should be true for other such LOS spells being sustained. It could be either Levitate specific for some crazy reason, or true of all LOS spells (and just not mentioned thanks to committee based rules design and all the other problems with the rules-writing in the game). They have changed the metaphysics of the game world in 6E, so nothing can be assumed any more. There are no more Limited Range spells, only Limited Duration spells, which is completely new and unprecedented (for a good reason--"fire and forget" spells are one of the very poor rules decisions in 6E). So you really are left guessing at the intent here. There's no wrong answer.
Instead, the answer is: Like most of 6E, it's up to your GM to write the rule until and unless the designers decide to do so.
Good luck!