I certainly don't think it's laziness.. seeing that they were mostly minted by slaves I doubt they were allowed to be lazy. Being manually produced .. while at the same time being under great pressure to produce as quickly as possible (sometimes in travelling mints) leads to poor workmanship. Especially at times of war... which was pretty much all the time. I believe the weight and purity would have been the prime focus rather than strike. I would also wager that the slaves doing the "striking" would be of the less skilled variety, easily replaceable and thrown into the job if they had finished other tasks (untrained) - as opposed to those artisans carving the die or those skilled workers creating and preparing the flans. (Cited from: https://www.cointalk.com/threads/why-are-so-many-ancients-so-far-off-center.345056/)
I think it has to do with the way they were struck. At an ANA Seminar in CO they were striking coins the old by-hand way. In order to make a decent looking piece, the operation was very slow because they had to be sure the two dies and planchet lined up to begin with. If the hammer was not brought down perfectly that could also cause so slip to the design.
…there was no collar like in modern minting.
…remember that there is no such thing as the 'ancient' way of doing things. Some dies were hinged; some anvil dies were concave making it easier to seat a blank. Some coins were struck hot making tongs needed; some were cold. I suspect at some point someone invented other ways of aligning dies but such technology may never have become widespread. Finding a coin of Aurelian which was not hinged means nothing when studying the coins of Tetricus (let alone Archaic or medieval coins).
I think the answer lies in the difficulty of the process and the minting goals. I think they were worried about the number of coins per pound (As) of silver and number of coins produced per day. Coins that were off center, brokage, unevenly struck or from worn dies circulated for a long time. It would be hard, and dangerous, to hold a small, hot flan; the punch die and strike with a small pointed hammer.
the flan placer was so concerning about this fingers that he used a pair of tongs…the loss of dexterity in using tongs would very likely increase miss hits.
I'll bet getting the weight of the planchet in tolerance was more important than what it looked like. After all, the design indicated the lump of metal was "OK" (just like the first ancient coins - (?) Lydians.) if most of it were showing, that's all that was needed.