Covering the second point first - The Rams drafted Mannion, then Goff the next season. They've had no reason to draft somebody, especially since McVay was wanting to rebuild the roster. He has done that substantially, AND Mannion is gone now. They have Bortles for a season, thanks to Jacksonville paying him $5.5 million making him very inexpensive for a vet backup.
But as
@OldSchool has pointed out (and others including myself in this thread have pointed out) the Rams are interviewing QBs. They have an interest in one.
You seem to be assuming that the Rams are stupid - that they can't tell the difference between a camp body and an actual prospect. They can - and Snead and McVay do know how expensive it would be to find a decent vet backup. Hence the need to develop a young guy to backup. It saves enough cap space to sign or keep a good but not great starter at many positions. Between that common sense realization, and the fact that they are interviewing a number of QBs, tells me that they want another QB to develop.
Maybe they don't find one - maybe everybody they like gets picked too early for their tastes. But they ARE looking - the interviews, the fact they just lost their inexpensive backup and lucked out in finding a one year signing tells most of us that they are looking.
Why didn't they look before? They were building up the rest of the lineup, and didn't need to before last season. Last year they drafted 11 guys, and spent the season developing them. Now is the time to bring in the backup QB of the future. They could wait forever, hoping they get lucky with a UDFA - but that hasn't exactly worked so far. Allen is a weak backup - he hasn't shown anything, and no team was interested in him when he was cut last season. Wolford had no interest in him for a practice squad last season, and was tied for fourth in QBs being signed from the AAF - not a ringing endorsement, since the AAF was full of players that no team wanted on their practice squad. Neither Allen nor Wolford are likely to stand in the way of the Rams pursuing another player. This is the NFL. every single team every single offseason signs players, and ends up cutting some of them not just before training camp, but sometimes before even any post-draft runthrough. This is normal - sign some kid just in case you don't get what you want later on. The signing bonuses are small and insignificant compared to the cap - basically rounding errors.