This study investigates the optical properties of WS2 and WSe2 monolayers and multilayers, focusing on the impact of symmetry variations and spin-valley coupling. The efficiency of second harmonic generation (SHG) shows a dramatic even-odd oscillation with the number of layers, indicating the presence or absence of inversion symmetry. Photoluminescence (PL) measurements reveal a crossover from an indirect band gap semiconductor in multilayers to a direct-gap one in monolayers. A hot luminescence peak (B) is observed at ~0.4 eV above the prominent band edge peak (A) in all samples, with the magnitude of A-B splitting being independent of the number of layers and coinciding with the spin-valley coupling strength in monolayers. Ab initio calculations confirm that this thickness-independent splitting pattern is a direct consequence of the strong spin-valley coupling, which suppresses interlayer hopping at the valence band edge near K points due to the sign change of the spin-valley coupling in the 2H stacking order. The study highlights the unique properties of tungsten dichalcogenides, making them promising materials for spintronics and valley-based electronics.This study investigates the optical properties of WS2 and WSe2 monolayers and multilayers, focusing on the impact of symmetry variations and spin-valley coupling. The efficiency of second harmonic generation (SHG) shows a dramatic even-odd oscillation with the number of layers, indicating the presence or absence of inversion symmetry. Photoluminescence (PL) measurements reveal a crossover from an indirect band gap semiconductor in multilayers to a direct-gap one in monolayers. A hot luminescence peak (B) is observed at ~0.4 eV above the prominent band edge peak (A) in all samples, with the magnitude of A-B splitting being independent of the number of layers and coinciding with the spin-valley coupling strength in monolayers. Ab initio calculations confirm that this thickness-independent splitting pattern is a direct consequence of the strong spin-valley coupling, which suppresses interlayer hopping at the valence band edge near K points due to the sign change of the spin-valley coupling in the 2H stacking order. The study highlights the unique properties of tungsten dichalcogenides, making them promising materials for spintronics and valley-based electronics.