Everyone does, but the insinuation that mp3s are anywhere close to an equivalent in sound quality of vinyl or CDs is just wrong.
The reason why they went with CDs this time around is that it is a multiple-item set. Producing a multiple-item set on vinyl is a VERY expensive undertaking - twice the packaging, twice the vinyl, increased cost of postage to be shipped worldwide, endless complaints from the list that they still haven’t gotten their sets (since their track record for shipping out vinyl speedily isn’t very good), etc. Thus, it was a completely rational decision to go with CDs this time; the overall cost of the set from start to finish is much more reasonable (and, ostensibly, we will get them without the months of delay).
I’m very happy that U2.com has changed their ways recently and hasn’t continued to follow the goofy reasoning used by the record industry at large where they just release things on vinyl and lazily lob an mp3 at those who don’t want vinyl. When they release single vinyls here, they now offer WAV downloads in addition to mp3 - that thinking shows they care about those who want better sound quality. I further hope that someday they offer lossless downloads as an option for these gifts (with artwork, of course) - those have better sound quality than all three formats mentioned above.
However, back to the topic at hand, simple cost in the production and mailing makes it CDs this time; vinyl has had a good run in gifts over the past 3-4 years - no doubt it will come back in the future too.