I've come across 1. e3 from one of my regular opponents quite often. These are my observations for why White might like this line:

1. Psychological: White plays a non-theoretical, flexible opening that White is likely to have played far more than Black.
2. Familiarity with an opening uses clock time more efficiently. Black may have to spend more time on the opening moves to check that there are no tactical deficiencies
3. As you rightly state, the move liberates the Queen & Bishop
4. Transpo tricks: White has the opportunity to transpo to English, reversed French, reversed Dutch & Queen pawn openings, e.g. the Colle
5. Solidity: White has a solid structure which facilitates safe development & early castling

The Van't Krujis leads to many opening lines, the named ones from Wikipedia are:

Keoni-Hiva Gambit: 1.e3 d5 2.Nc3 Nf6 3.a3 e5 4.f4 exf4 5.Nf3

• White gambits he pawn to castle kingside & target f7
• White often plays b5 to either fianchetto the queen side bishop to attack the king side
• Black sometimes jettisons the d5 pawn to the c3 knight with Nxd5 to reduce White's initiative
• Also, 3. a3 prevents a disruptive Bb4, threatening to remove the knight & simplifying when Black will soon be up a pawn

Amsterdam Attack: 1.e3 e5 2.c4 d6 3.Nc3 Nc6 4.b3 Nf6

• This is a transposition to the English opening, Bremen line

Ekolu Variation: 1.e3 e5 2.Nc3 d5 3.f4 exf4 4.Nf3

• Similar analysis to the Keoni-Hiva Gambit

Alua Variation: 1.e3 e5 2.Nc3 Nc6 3.f4 exf4 4.Nf3

• Similar analysis to the Keoni-Hiva Gambit

Akahi Variation: 1.e3 e5 2.Nc3 Nf6 3.f4 exf4 4.Nf3

• Similar analysis to the Keoni-Hiva Gambit

Bouncing Bishop Variation: 1.e3 e5 2.Bc4 d5 3.Bb3

• White aims to pressure the centre & Black's kingside with the Bishop on b3, similar to lines of the Ruy Lopez where White plays Bf1-b5-a4-b3

I've come across 1. e3 from one of my regular opponents quite often. These are my observations for why White might like this line:

1. Psychological: White plays a non-theoretical, flexible opening that White is likely to have played far more than Black.
2. Familiarity with an opening uses clock time more efficiently. Black may have to spend more time on the opening moves to check that there are no tactical deficiencies
3. As you rightly state, the move liberates the Queen & Bishop
4. Transposition tricks: White has the opportunity to transpose to the English, reversed French, reversed Dutch & Queen pawn openings, e.g. the Colle
5. Solidity: White has a solid structure which facilitates safe development & early castling

The Van't Krujis leads to many opening lines, the named ones from Wikipedia are:

[title "Keoni-Hiva Gambit"]    
[fen ""]

1.e3 d5 2.Nc3 Nf6 3.a3 e5 4.f4 exf4 5.Nf3

• White gambits the pawn to castle kingside & target f7
• White often plays b5 to either fianchetto the queen side bishop to attack the king side
• Black sometimes jettisons the d5 pawn to the c3 knight with Nxd5 to reduce White's initiative
• Also, 3. a3 prevents a disruptive Bb4, threatening to remove the knight & simplifying when Black will soon be up a pawn

and

[title "Amsterdam Attack"]    
[fen ""]

1.e3 e5 2.c4 d6 3.Nc3 Nc6 4.b3 Nf6

• This is a transposition to the English opening, Bremen line

and

[title "Ekolu Variation"]    
[fen ""]

1.e3 e5 2.Nc3 d5 3.f4 exf4 4.Nf3

• Similar analysis to the Keoni-Hiva Gambit

and

[title "Alua Variation"]    
[fen ""]

1.e3 e5 2.Nc3 Nc6 3.f4 exf4 4.Nf3

• Similar analysis to the Keoni-Hiva Gambit

and

[title "Akahi Variation"]    
[fen ""]

1.e3 e5 2.Nc3 Nf6 3.f4 exf4 4.Nf3

• Similar analysis to the Keoni-Hiva Gambit

and

[title "Bouncing Bishop Variation"]    
[fen ""]

 1.e3 e5 2.Bc4 d5 3.Bb3

• White aims to pressure the centre & Black's kingside with the Bishop on b3, similar to lines of the Ruy Lopez where White plays Bf1-b5-a4-b3