[Nextgrid]

Most document signing solutions out there use no cryptography and are equivalent to someone claiming that someone else signed something. In this case, short of actual cryptography, you'd at least want the claimant to be a neutral, unbiased third-party - a self-hosted solution would raise lots of issues because you will be able to trivially and retroactively falsify signatures or documents.

[ElTimuro]

Good point. Cryptography can be a remedy here, but this is still a relevant factor IMO