If it is a good game I have no problem to buy it a second time, especially if it is a better version (higher resolution, better fps/frametimes, 4K textures, more or better effects/shaders...) or adds nice features (f.e. portability, convenience).But I don't buy two versions for the full price, the second has to be on sale.
I bought hundreds of classics digitally (GOG, Steam, PS store...) on sales although I still have the disc. And thanks to bundles and PS+ I have hundreds more modern games on different platforms.
Duplicate Steam keys from bundles I usually gift to Steam friends... the participants of the annual Secret Santa can vouch for that
Of course I prefer it, if I get the second version (legally) for free... on Steam you get the remastered version often for free, if you bought the original (Skyrim, BioShock 1 & 2, Darksiders 1 + 2, The Vanishing of Ethan Carter, The Raven, The Whispered World...)
Cross-buy in the PS Store was also a great thing (while it lasted): one version optimized for the handheld and one version optimized for the faster home console hardware.
Today all Kickstarter backers of "Shantae: Half-Genie Hero" got a free Steam code for the Ultimate Edition (includes all DLC and other extras) additional to their chosen platform. Now I can play Shantae: Half-Genie Hero with all DLCs on my Vitas on the go and on my PC in 4K at home. All I payed back then was €11 and I got the main game + all DLCs (worth €40 to €55 depending on the platform) + backer exclusive content + the Ultimate Edition (probably around 30 bucks) on a second platform! And backers could play the main game and each DLC one week before the official release.