We've also had unsealed cards arrive with mangled envelopes this year, inevitable if they're going through sorting machines I expect.
We used a kitchen sponge to seal ours, resorting to sellotape if all the gum came off. None of our cards had the self seal strips.
My frugal mother used to save the stickers from the Spastics Society and then seal her cards with them. She was still using them many years after the more PC "Scope" came into being, my children loved the joke when they received them. After she died there were enough left for me to use them on their cards for a couple more years.
Another Tory MP crosses the floor