In addition to @dm63 answer, I recall the primary concern in the repo space was the impact to the 'exposure measure' in the regulatory Leverage Ratio (LR). Globally Systemic banks (in different jurisdictions) have historically had relatively tough minimum requirements for the LR (6% in the US), which leaves a 2 or 3 tick profit (or 200k per 1bn notional), regardless of the maturity of the bond, particularly unappealing, especially compared to other potential allocations of the capital.
If you consider the return on capital employed, since 6% of capital is required per exposure (in the worst case) this trade (if the exposure is increased by 1bn) requires 60mm capital. The return of 200k is 0.33%.
Even if you take the best case where only 3% of capital is required and the return is 0.66%. This is still pretty useless: I have seen an investment bank turn down trades which yield 5% return on capital regularly.
From what I remember about net basis trading (going back 10 years) it was also something that many people struggled to fully appreciate the nuances of managing the risk.
If I remember correctly you had to calculate the specific amount of futures that were needed on an ongoing basis (i.e. to hedge MTM) and then going into settlement (EDSP) you needed to trade additional futures lots to ensure your notionals for delivery matched.
If you get that wrong those 2 or 3 ticks disappear away fairly easily.