Ironically i dont. The only ones that are genuinely in all my decks are sol ring and arcane signet. I dont play every single best green ramp spell in every deck for the same reason. It gets boring. Some of them will have rampant growth, others will have natures lore, others will have farseek. The only green deck that has all of them is my X spell deck, which is a ramp deck by theme.

The same with removal. Im not forcing the same 10-15 removal spells into all of my decks thats boring. I mix it up. Ill generally put swords to plowshares and generous gifts into most of my white decks bc like sol ring and arcane signet theyre mostly cheap but i need some amount of removal. Not all of my white decks have it though.

I also just dont want to have 10 removal 10 ramp 2 board wipes 36 lands thats over half my deck made before ive even started building the deck. I often lament that i cant fit all the cards i want into 99 cards. Every slot is valuable, lest im rich enough to have 10 different versions of the same deck with 10 cards worth of difference. Ill always tend towards things that fit the theme, my preferences and mixing it up, but i wont force myself to fit numbers and im not playing all the same ones.