Warlocks that focus on Elderich Blast want two things: to cast Eldritch blast every round, and have a consistent use of their bonus action.

Normally hex occupies that bonus action and because it scales with number of attacks it scales with level as Elderich blast increases the number of beams moving from 1d6 all the way up to 4d6 at level 17. Hex doesn't scale with spell level apart from duration which is irrelevant to warlock as they get their spells back on a short rest anyway.

The new Spiritual Weapon also uses concentration and increases 1d8 in damage for each spell level meaning that by level 9 warlocks can get an effective 4d8+spell mod out of it rather than 4d6 without Cha mod by level 17. That's essentially 9 more dpr at level 9 vs with hex at level 17.

Is this a case that Spiritual weapons is a good? Probably not but it really demonstrates how bad Hex is most of the time.

No, hex is bad past early levels.

A not super optimal but interesting one is hexing with great old one at 10 to have it reduce saves + mind sliver does too seems handy

unless is Great old one warlock,eldrich hex is legit best debuff on the game

If you're willing to pick up Magic Connoisseur, then Spiritual Weapon would probably be an upgrade. At worst it'd be a sidegrade, and that's only because the 20 ft movement makes it harder to use. But, well, there are frankly better things you could be spending your Concentration on than either spell.

Vestige Warlock can also acquire Spiritual Weapon, but it's not great on them since their Bonus Action is already preoccupied by commanding the Vestige.

Ok sure but that's the power of that subclass feature not the base hex spell

Eldritch hex + finger of death

If you have Hexblood, you can do Eldritch Hex for 1 minute for free per day.

Not better than bane, or synaptic static through.

Ice knife also procs both save and attack roll.

Why the F would a warlock have a Spiritual Weapon?!

Vestige warlock or Magic Consueseur

add disvantage to a saving throw is pretty strong

Sure but it's single target and uses concentration. Bane also uses concentration but can effect multiple targets and synaptic static has both no concentration does damage debuffs and targets a weak save

Spiritual weapon's movement speed can be surprisingly limiting, particularly in dynamic fights and later tiers where important threats are fast or hang back with frontline allies.

No, I mean it’s a warlock. Why would a warlock use a SPIRITUAL weapon?