Prerequisites:

- Make sure that you have WebGL platform support installed
- (Optional) Make sure that you have Desktop, Android, and iOS platform support packages installed

Steps to reproduce:

1. Download and open the attached project (New Unity Project.zip)
2. Open SampleScene
3. Navigate to File > Build Settings
4. Switch to WebGL platform
5. Bake lighting
6. Select lightmap texture
7. Enable Crunch Compression bool in the texture importer settings
8. Notice that it has no effect neither to its visual quality, nor size

Notes:

- Does not reproduce in: 2019.2.11f1, 2019.2.21f1, 2019.4.37f1 (Note: only because the textures end up using DXT in 2019.4\! Not a regression.)
- Reproduces in: 2020.3.31f1, 2021.2.17f1 and newer builds (non-DXT formats are used, so crunch cannot be used)
- It affects other platforms as well, to a degree. Will share more information in the comments section
- The causal factor could be texture format incompatibility with the crunch compression algorithm
- In an ideal case scenario, all texture formats should work well with the crunch compression algorithm
- In cases where that's not possible, crunch compression bool should be inactive